It's a general-purpose tool, so we expect to see all kinds of things built.

I'm especially excited about location services -- our SF Live Bus example in the blog post is one example, but in general there are tons of applications for notifying others of the locations of things in real-time (Uber, Postmates, Lyft, etc). I'm also very excited about multiplayer gaming on mobile, which is still in it's infancy. Some of the more interesting ones use phones in new ways. Gempad (in the post) uses your phone as essentially another input device. There are a bunch of other cool things you could do here as well.