diff -r 000000000000 -r 6474c204b198 browser/devtools/app-manager/simulators-store.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/app-manager/simulators-store.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,21 @@
+/* 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 ObservableObject = require("devtools/shared/observable-object");
+const {Simulator} = Cu.import("resource://gre/modules/devtools/Simulator.jsm");
+
+let store = new ObservableObject({versions:[]});
+
+function feedStore() {
+  store.object.versions = Simulator.availableVersions().map(v => {
+    return {version:v}
+  });
+}
+
+Simulator.on("register", feedStore);
+Simulator.on("unregister", feedStore);
+feedStore();
+
+module.exports = store;