Figure iPad interface suggestion
As I was playing Reason on the iPad, especially the bass and synth, it would feel more natural for the full screen playing surface to run diagonal, or better yet radially, for one hand to play notes, leaving space in the upper corner for pitch and a smaller tweak control, so you can tweak while you play.
The radially curved surface running diagonally would make it easier to play, but also make room for a few more notes.
Other than that what you guys came up with is a new form of instrument. It would be cool to use the same interface to trigger and manipulate video.