The Ocarina of iPhone?

from MAKE Magazine by Collin Cunningham: The Ocarina synthesizes sound in real-time, just like a regular instrument, based on actual gestures including wind input, tilt, and finger placement over the four holes overlaid on the multi-touch pad. Unlike other iPhone audio apps, the sound is not pre-compiled but is generated by the notes, gestures and nuance of the individual performer. As a result, it allows an iPhone user to explore and master the musical sounds of an entirely iPhone-native version of an ancient flute-like instrument.