Curling up in a ball and rolling around on the floor seems like a worst case for a lot of motion tracking setups. Systems based on wearable sensors won't work because you can't comfortably roll around in them, and single-viewpoint systems like the Kinect get confused when they can't see your whole body.

Have you tried getting a bunch of Kinects and doing some kind of sensor fusion? I don't know what the current state of the software is but you can buy the hardware for <$100 each used.