Soundboxing is a music rhythm game very similar to Audioshield. The big difference with Soundboxing, is that you make user created beat-maps to play, or you play previously created beat-maps by other players. The game works with YouTube in such a way, that it allows you to search for just about any song in existence, and then create a special beat-map for it. You can also search through already existing beat-maps and try those. Beatmap creation can be quite fun,  but it's also a very tiring process. You're literally punching into thin air to make the beat-maps. In fact, Soundboxing is probably one of the better exercise games out there. I'd probably put it up there with Holopoint as being one of the better accidental exercise options. The game is only $8, which makes it a solid value as well.