Harmonica is a little app created by Benjamin McDowell, developed in the same vein as Ocarina. It’s designed to be used like a real harmonica.
Just like the real thing, you place the iPhone in your mouth and slide from side to side to play notes. There are two buttons which allow you to choose from chords or draw notes, widening the app’s capabilities. If, for some reason, you don’t like the idea of placing dirty electronic devices in your mouth, you can play with your finger as well.
While I can’t say Harmonica is terribly useful, you’ll get some novelty fun out of it for a while.