I found a game on WP 7 called Song Arc. Its basically like any other rhythm game (like guitar hero), only it uses the songs on your phone. The music sheets are user created, so some of them suck pretty badly, but I have found some that are actually really good. Its a great way to waste long periods of time. I haven't tried creating my own sheet yet (it seems complicated), but I might give it a shot. Anyone play this yet?