The Wii Drum Kit is another great example of a tangible user interface made possible with the Wiimote. The latest version adds support for the Nunchuck, so you can use both hands to play your virtual drum kit. This one is a Windows application, and source is available at the This is Not a Label blog.
The Wiimote + Nunchuck combination seems like the perfect interface for an air drum. Different gestures are used to trigger a specific drum, so the high hat is a flick to the side, the snare is a forward hit, etc. There’s no kick pedal, of course, but the fist stamping motion that’s used is a reasonable alternative.