Run firefox OS on your Android Phone
Mozilla has released the Firefox OS 2.5 Developer Preview which you can try on your Android phone just like any other app.
The Firefox OS 2.5 has released apk which you can install on your Android device and by pressing home button it will start as new Home screen.
Going back to older home screen you can use ur Android as is.
Visit Mozilla Blog for more details. You can download apk from here.