Not much on their homepage aside from the above video, but here it is for safe keeping.

The guy on the iPhone is using the just-released iAno, by mister.aardvark. iAno features a complete keyboard (you can navigate up and down octaves using the buttons above the keys) and the ability to play chords thanks to the multitouch capability of the iPhone.

The 2nd iPhone player is using PocketGuitar, another recently developed app.

The DS is running Electroplankton in performance mode, with the plankton of choice being the Luminaria, little guys that follow a user-defined path on a grid (you can see him set up the paths at the beginning of the above video).

Bah, as I was finishing this up, I noticed that the instruments were listed on the gizmodo post that started the whole thing. Oh well, figuring em out was still fun.