SynthPond is a sort of audio exploration toy app for iPhone by Zach Gage. It really brings to mind a very complex and highly customizable windchime. I’m not quite sure how else to describe it without getting into a more technical explanation, but I don’t think it’s necessary. Even without understanding everything that’s going on, it is still highly entertaining and beautiful to watch.
There’s a very detailed writeup of it on the CreativeApplications blog with additional screenshots, video, and in depth details about what SynthPond can do. While you’re at that site I recommend taking a look around. There’s lots of other great iPhone apps reviewed there and other non-iPhone-related geeky creative coolness.