Beatstream is the latest app from the folks at Smule (who recently acquired Khush, another music-loving developer, and I can kind of see their influence here as well). Usually, Smule's apps are based around creation of music, but Beatstream is a little more targeted towards listening to your music (at least at first). The idea is that you can pull any music from your iTunes library, and Beatstream will turn it into a game, the game-iest game that I've ever seen Smule make. You basically control an arrow running along a path, and you can tap on the screen to flip it through two different colors, which match barriers running along the path in front of you. The goal is to make sure that when your little arrow crosses the barriers, it's the same color. Matching colors and going through levels you up, and missing the colors brings you back down.
It's fun, and even on the easiest setting, the barriers show up on the screen quickly enough that there is a little bit of a challenge trying to make sure the arrow is flipped the right way before going through them. There are also badges to earn, and unlike standard achievements, these actually change the gameplay a little bit, or even trip up the way the music sounds, like making it go faster or play in some crazy fashion.
The one caveat with the music in Beatstream is that, like all other apps that pull music from your library, it won't work with DRM-protected songs, so if there's anything on your device from before 2009, you might not be able to play it. Same deal with long songs -- I had a few really long songs that just didn't work. But I was able to get a shorter song working without a problem, and while you could tell the song was matched with an algorithm (rather than by hand, like a Rock Band or Guitar Hero song), it still played well along with the music anyway.
Beatstream is a cool way to experience your music while tapping along with that little arrow. I don't think it'll be a tentpole release for Smule -- it doesn't quite have that music creation streak that has led them to so much success with apps like Ocarina and Magic Piano. But it's a quality addition to their library for sure -- it's 99 cents on the App Store right now.