I'm hoping to try this approach with a digital piano keyboard. Will it be usable if I can see the keys but not see my hands? I'll find out. (I'm not a very good player, I can play without looking at the keys but I still need to glance at them, e.g. when changing position or playing a wide chord)

edit to note: I do have a Leap Motion, and I'll try that, too, but right now my plan is to use it above the keyboard as a gesture controller rather than facing down at the keys. Lots of experiments to try. :)