Peter Daukintis shared with us drums hack built using OpenNI framework http://www.openni.org/ with PrimeSense NITE components.
This is roughly how the demo was made:
- modification of the NITE c++ sample which does user tracking (Players) to track multiple users
- wrapping this in a c+/cli component for consumption in a .NET environment
- consumed the .NET component in a WPF 3D desktop application