MB isn't really mobile compatible. If you try to build on a mobile device, you can see how hard it is. (in a browser of course)
You can go all around the site and all (I do it all the time), but the Workshop is difficult to use. If you really want a MB app the closest you can get, is to add the website (bookmark) to your home screen.
You can check out this topic I started the other day questioning MB's "mobileness". http://mecabricks.com/en/forum/topic/493