diff --git a/browser/devtools/webide/modules/runtimes.js b/browser/devtools/webide/modules/runtimes.js
index d6d828cc31d..f6c3cf7ef20 100644
--- a/browser/devtools/webide/modules/runtimes.js
+++ b/browser/devtools/webide/modules/runtimes.js
@@ -5,9 +5,9 @@
 const {Cu, Ci} = require("chrome");
 const {Devices} = Cu.import("resource://gre/modules/devtools/Devices.jsm");
 const {Services} = Cu.import("resource://gre/modules/Services.jsm");
-const {Simulator} = Cu.import("resource://gre/modules/devtools/Simulator.jsm");
-const {ConnectionManager, Connection} = require("devtools/client/connection-manager");
+const {Connection} = require("devtools/client/connection-manager");
 const {DebuggerServer} = require("resource://gre/modules/devtools/dbg-server.jsm");
+const {Simulators} = require("devtools/webide/simulators");
 const discovery = require("devtools/toolkit/discovery/discovery");
 const EventEmitter = require("devtools/toolkit/event-emitter");
 const promise = require("promise");
@@ -193,14 +193,12 @@ let SimulatorScanner = {
 
   enable() {
     this._updateRuntimes = this._updateRuntimes.bind(this);
-    Simulator.on("register", this._updateRuntimes);
-    Simulator.on("unregister", this._updateRuntimes);
+    Simulators.on("updated", this._updateRuntimes);
     this._updateRuntimes();
   },
 
   disable() {
-    Simulator.off("register", this._updateRuntimes);
-    Simulator.off("unregister", this._updateRuntimes);
+    Simulators.off("updated", this._updateRuntimes);
   },
 
   _emitUpdated() {
@@ -208,11 +206,13 @@ let SimulatorScanner = {
   },
 
   _updateRuntimes() {
-    this._runtimes = [];
-    for (let name of Simulator.availableNames()) {
-      this._runtimes.push(new SimulatorRuntime(name));
-    }
-    this._emitUpdated();
+    Simulators.getAll().then(simulators => {
+      this._runtimes = [];
+      for (let simulator of simulators) {
+        this._runtimes.push(new SimulatorRuntime(simulator));
+      }
+      this._emitUpdated();
+    });
   },
 
   scan() {
@@ -542,28 +542,26 @@ WiFiRuntime.prototype = {
 // For testing use only
 exports._WiFiRuntime = WiFiRuntime;
 
-function SimulatorRuntime(name) {
-  this.name = name;
+function SimulatorRuntime(simulator) {
+  this.simulator = simulator;
 }
 
 SimulatorRuntime.prototype = {
   type: RuntimeTypes.SIMULATOR,
   connect: function(connection) {
-    let port = ConnectionManager.getFreeTCPPort();
-    let simulator = Simulator.getByName(this.name);
-    if (!simulator || !simulator.launch) {
-      return promise.reject(new Error("Can't find simulator: " + this.name));
-    }
-    return simulator.launch({port: port}).then(() => {
+    return this.simulator.launch().then(port => {
       connection.host = "localhost";
       connection.port = port;
       connection.keepConnecting = true;
-      connection.once(Connection.Events.DISCONNECTED, simulator.close);
+      connection.once(Connection.Events.DISCONNECTED, e => this.simulator.kill());
       connection.connect();
     });
   },
   get id() {
-    return this.name;
+    return this.simulator.id;
+  },
+  get name() {
+    return this.simulator.name;
   },
 };
 
diff --git a/browser/devtools/webide/modules/simulator-process.js b/browser/devtools/webide/modules/simulator-process.js
new file mode 100644
index 00000000000..0ebae120b0e
--- /dev/null
+++ b/browser/devtools/webide/modules/simulator-process.js
@@ -0,0 +1,273 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+'use strict';
+
+const { Cc, Ci, Cu } = require("chrome");
+
+const Environment = require("sdk/system/environment").env;
+const Subprocess = require("sdk/system/child_process/subprocess");
+const { EventEmitter } = Cu.import("resource://gre/modules/devtools/event-emitter.js", {});
+const { Promise: promise } = Cu.import("resource://gre/modules/Promise.jsm", {});
+const { Services } = Cu.import("resource://gre/modules/Services.jsm", {});
+
+let platform = Services.appShell.hiddenDOMWindow.navigator.platform;
+let OS = "";
+if (platform.indexOf("Win") != -1) {
+  OS = "win32";
+} else if (platform.indexOf("Mac") != -1) {
+  OS = "mac64";
+} else if (platform.indexOf("Linux") != -1) {
+  if (platform.indexOf("x86_64") != -1) {
+    OS = "linux64";
+  } else {
+    OS = "linux32";
+  }
+}
+
+function SimulatorProcess() {}
+SimulatorProcess.prototype = {
+
+  // Check if B2G is running.
+  get isRunning() !!this.process,
+
+  // Start the process and connect the debugger client.
+  run() {
+
+    // Resolve B2G binary.
+    let b2g = this.b2gBinary;
+    if (!b2g || !b2g.exists()) {
+      throw Error("B2G executable not found.");
+    }
+
+    this.once("stdout", function () {
+      if (OS == "mac64") {
+        console.debug("WORKAROUND run osascript to show b2g-desktop window on OS=='mac64'");
+        // Escape double quotes and escape characters for use in AppleScript.
+        let path = b2g.path.replace(/\\/g, "\\\\").replace(/\"/g, '\\"');
+
+        Subprocess.call({
+          command: "/usr/bin/osascript",
+          arguments: ["-e", 'tell application "' + path + '" to activate'],
+        });
+      }
+    });
+
+    this.on("stdout", (e, data) => this.log(e, data.trim()));
+    this.on("stderr", (e, data) => this.log(e, data.trim()));
+
+    let environment;
+    if (OS.indexOf("linux") > -1) {
+      environment = ["TMPDIR=" + Services.dirsvc.get("TmpD", Ci.nsIFile).path];
+      if ("DISPLAY" in Environment) {
+        environment.push("DISPLAY=" + Environment.DISPLAY);
+      }
+    }
+
+    // Spawn a B2G instance.
+    this.process = Subprocess.call({
+      command: b2g,
+      arguments: this.args,
+      environment: environment,
+      stdout: data => this.emit("stdout", data),
+      stderr: data => this.emit("stderr", data),
+      // On B2G instance exit, reset tracked process, remote debugger port and
+      // shuttingDown flag, then finally emit an exit event.
+      done: result => {
+        console.log("B2G terminated with " + result.exitCode);
+        this.process = null;
+        this.emit("exit", result.exitCode);
+      }
+    });
+  },
+
+  // Request a B2G instance kill.
+  kill() {
+    let deferred = promise.defer();
+    if (this.process) {
+      this.once("exit", (e, exitCode) => {
+        this.shuttingDown = false;
+        deferred.resolve(exitCode);
+      });
+      if (!this.shuttingDown) {
+        this.shuttingDown = true;
+        this.emit("kill", null);
+        this.process.kill();
+      }
+      return deferred.promise;
+    } else {
+      return promise.resolve(undefined);
+    }
+  },
+
+  // Maybe log output messages.
+  log(level, message) {
+    if (!Services.prefs.getBoolPref("devtools.webide.logSimulatorOutput")) {
+      return;
+    }
+    if (level === "stderr" || level === "error") {
+      console.error(message);
+      return;
+    }
+    console.log(message);
+  },
+
+  // Compute B2G CLI arguments.
+  get args() {
+    let args = [];
+
+    let gaia = this.gaiaProfile;
+    if (!gaia || !gaia.exists()) {
+      throw Error("Gaia profile directory not found.");
+    }
+    args.push("-profile", gaia.path);
+
+    args.push("-start-debugger-server", "" + this.options.port);
+
+    // Ignore eventual zombie instances of b2g that are left over.
+    args.push("-no-remote");
+
+    return args;
+  },
+};
+
+EventEmitter.decorate(SimulatorProcess.prototype);
+
+
+function CustomSimulatorProcess(options) {
+  this.options = options;
+}
+
+let CSPp = CustomSimulatorProcess.prototype = Object.create(SimulatorProcess.prototype);
+
+// Compute B2G binary file handle.
+Object.defineProperty(CSPp, "b2gBinary", {
+  get: function() {
+    let file = Cc['@mozilla.org/file/local;1'].createInstance(Ci.nsILocalFile);
+    file.initWithPath(this.options.b2gBinary);
+    return file;
+  }
+});
+
+// Compute Gaia profile file handle.
+Object.defineProperty(CSPp, "gaiaProfile", {
+  get: function() {
+    let file = Cc['@mozilla.org/file/local;1'].createInstance(Ci.nsILocalFile);
+    file.initWithPath(this.options.gaiaProfile);
+    return file;
+  }
+});
+
+exports.CustomSimulatorProcess = CustomSimulatorProcess;
+
+
+function AddonSimulatorProcess(addon, options) {
+  this.addon = addon;
+  this.options = options;
+}
+
+let ASPp = AddonSimulatorProcess.prototype = Object.create(SimulatorProcess.prototype);
+
+// Compute B2G binary file handle.
+Object.defineProperty(ASPp, "b2gBinary", {
+  get: function() {
+    let file;
+    try {
+      let pref = "extensions." + this.addon.id + ".customRuntime";
+      file = Services.prefs.getComplexValue(pref, Ci.nsIFile);
+    } catch(e) {}
+
+    if (!file) {
+      let binaries = {
+        win32: "b2g-bin.exe",
+        mac64: "B2G.app/Contents/MacOS/b2g-bin",
+        linux32: "b2g-bin",
+        linux64: "b2g-bin",
+      };
+      file = this.addon.getResourceURI().QueryInterface(Ci.nsIFileURL).file;
+      file.append("b2g");
+      file.append(binaries[OS]);
+    }
+    return file;
+  }
+});
+
+// Compute Gaia profile file handle.
+Object.defineProperty(ASPp, "gaiaProfile", {
+  get: function() {
+    let file;
+    try {
+      let pref = "extensions." + this.addon.id + ".gaiaProfile";
+      file = Services.prefs.getComplexValue(pref, Ci.nsIFile);
+    } catch(e) {}
+
+    if (!file) {
+      file = this.addon.getResourceURI().QueryInterface(Ci.nsIFileURL).file;
+      file.append("profile");
+    }
+    return file;
+  }
+});
+
+exports.AddonSimulatorProcess = AddonSimulatorProcess;
+
+
+function OldAddonSimulatorProcess(addon, options) {
+  this.addon = addon;
+  this.options = options;
+}
+
+let OASPp = OldAddonSimulatorProcess.prototype = Object.create(AddonSimulatorProcess.prototype);
+
+// Compute B2G binary file handle.
+Object.defineProperty(OASPp, "b2gBinary", {
+  get: function() {
+    let file;
+    try {
+      let pref = "extensions." + this.addon.id + ".customRuntime";
+      file = Services.prefs.getComplexValue(pref, Ci.nsIFile);
+    } catch(e) {}
+
+    if (!file) {
+      let version = this.addon.name.match(/\d+\.\d+/)[0].replace(/\./, "_");
+      file = this.addon.getResourceURI().QueryInterface(Ci.nsIFileURL).file;
+      file.append("resources");
+      file.append("fxos_" + version + "_simulator");
+      file.append("data");
+      file.append(OS == "linux32" ? "linux" : OS);
+      if (OS == "mac64") {
+        file.append("B2G.app");
+        file.append("Contents");
+        file.append("MacOS");
+      } else {
+        file.append("b2g");
+      }
+      file.append("b2g-bin" + (OS == "win32" ? ".exe" : ""));
+    }
+    return file;
+  }
+});
+
+// Compute B2G CLI arguments.
+Object.defineProperty(OASPp, "args", {
+  get: function() {
+    let args = [];
+
+    let gaia = this.gaiaProfile;
+    if (!gaia || !gaia.exists()) {
+      throw Error("Gaia profile directory not found.");
+    }
+    args.push("-profile", gaia.path);
+
+    args.push("-dbgport", "" + this.options.port);
+
+    // Ignore eventual zombie instances of b2g that are left over.
+    args.push("-no-remote");
+
+    return args;
+  }
+});
+
+exports.OldAddonSimulatorProcess = OldAddonSimulatorProcess;
diff --git a/browser/devtools/webide/modules/simulators.js b/browser/devtools/webide/modules/simulators.js
new file mode 100644
index 00000000000..2e05e91e615
--- /dev/null
+++ b/browser/devtools/webide/modules/simulators.js
@@ -0,0 +1,96 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const { Cu } = require("chrome");
+const { AddonManager } = Cu.import("resource://gre/modules/AddonManager.jsm");
+const { EventEmitter } = Cu.import("resource://gre/modules/devtools/event-emitter.js");
+const { ConnectionManager } = require("devtools/client/connection-manager");
+const { AddonSimulatorProcess, OldAddonSimulatorProcess } = require("devtools/webide/simulator-process");
+const promise = require("promise");
+
+const SimulatorRegExp = new RegExp(Services.prefs.getCharPref("devtools.webide.simulatorAddonRegExp"));
+
+let Simulators = {
+  // TODO (Bug 1090949) Don't generate this list from installed simulator
+  // addons, but instead implement a persistent list of user-configured
+  // simulators.
+  getAll() {
+    let deferred = promise.defer();
+    AddonManager.getAllAddons(addons => {
+      let simulators = [];
+      for (let addon of addons) {
+        if (SimulatorRegExp.exec(addon.id)) {
+          simulators.push(new Simulator(addon));
+        }
+      }
+      // Sort simulators alphabetically by name.
+      simulators.sort((a, b) => {
+        return a.name.toLowerCase().localeCompare(b.name.toLowerCase())
+      });
+      deferred.resolve(simulators);
+    });
+    return deferred.promise;
+  },
+}
+EventEmitter.decorate(Simulators);
+exports.Simulators = Simulators;
+
+function update() {
+  Simulators.emit("updated");
+}
+AddonManager.addAddonListener({
+  onEnabled: update,
+  onDisabled: update,
+  onInstalled: update,
+  onUninstalled: update
+});
+
+
+function Simulator(addon) {
+  this.addon = addon;
+}
+
+Simulator.prototype = {
+  launch() {
+    // Close already opened simulation.
+    if (this.process) {
+      return this.kill().then(this.launch.bind(this));
+    }
+
+    let options = {
+      port: ConnectionManager.getFreeTCPPort()
+    };
+
+    if (this.version <= "1.3") {
+      // Support older simulator addons.
+      this.process = new OldAddonSimulatorProcess(this.addon, options);
+    } else {
+      this.process = new AddonSimulatorProcess(this.addon, options);
+    }
+    this.process.run();
+
+    return promise.resolve(options.port);
+  },
+
+  kill() {
+    let process = this.process;
+    if (!process) {
+      return promise.resolve();
+    }
+    this.process = null;
+    return process.kill();
+  },
+
+  get id() {
+    return this.addon.id;
+  },
+
+  get name() {
+    return this.addon.name.replace(" Simulator", "");
+  },
+
+  get version() {
+    return this.name.match(/\d+\.\d+/)[0];
+  },
+};
diff --git a/browser/devtools/webide/moz.build b/browser/devtools/webide/moz.build
index e9804d09ca6..20a072793a9 100644
--- a/browser/devtools/webide/moz.build
+++ b/browser/devtools/webide/moz.build
@@ -20,6 +20,8 @@ EXTRA_JS_MODULES.devtools.webide += [
     'modules/config-view.js',
     'modules/remote-resources.js',
     'modules/runtimes.js',
+    'modules/simulator-process.js',
+    'modules/simulators.js',
     'modules/tab-store.js',
     'modules/utils.js'
 ]
diff --git a/browser/devtools/webide/webide-prefs.js b/browser/devtools/webide/webide-prefs.js
index 73a674449e9..6e21bec8b14 100644
--- a/browser/devtools/webide/webide-prefs.js
+++ b/browser/devtools/webide/webide-prefs.js
@@ -13,6 +13,7 @@ pref("devtools.webide.enableLocalRuntime", false);
 pref("devtools.webide.addonsURL", "https://ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/index.json");
 pref("devtools.webide.simulatorAddonsURL", "https://ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/#VERSION#/#OS#/fxos_#SLASHED_VERSION#_simulator-#OS#-latest.xpi");
 pref("devtools.webide.simulatorAddonID", "fxos_#SLASHED_VERSION#_simulator@mozilla.org");
+pref("devtools.webide.simulatorAddonRegExp", "fxos_(.*)_simulator@mozilla\.org$");
 pref("devtools.webide.adbAddonURL", "https://ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/adb-helper/#OS#/adbhelper-#OS#-latest.xpi");
 pref("devtools.webide.adbAddonID", "adbhelper@mozilla.org");
 pref("devtools.webide.adaptersAddonURL", "https://ftp.mozilla.org/pub/mozilla.org/labs/fxdt-adapters/#OS#/fxdt-adapters-#OS#-latest.xpi");
@@ -20,6 +21,7 @@ pref("devtools.webide.adaptersAddonID", "fxdevtools-adapters@mozilla.org");
 pref("devtools.webide.monitorWebSocketURL", "ws://localhost:9000");
 pref("devtools.webide.lastConnectedRuntime", "");
 pref("devtools.webide.lastSelectedProject", "");
+pref("devtools.webide.logSimulatorOutput", false);
 pref("devtools.webide.widget.autoinstall", true);
 #ifdef MOZ_DEV_EDITION
 pref("devtools.webide.widget.enabled", true);