Check outcheap motion capture system. Well, relatively cheap that is. It still costs about three thousand dollars.
“Video games like Dance Dance Revolution could soon require more than just fancy footwork. Small, cheap sensors for tracking the movement of a person’s entire body could lead to “whole-body interfaces” for controlling computers or playing games, researchers say.”
There is an article and demo video here:
http://technology.newscientist.com/article/dn12963-cheap-sensors-could-capture-your-every-move.html