It's funny because we were brainstorming on the hoop the other night and it hit me that this was the killer app for a "cheap and cheerful" inertial navigation system.
The Trident 2 submarine missile has a gyroscope in it that costs almost as much as the nuclear warhead because it is so resistant to drift that it can be spun up and locked on in port and maintain its position when the submarine is at sea.
If you tried INS with a smart phone or wiimote the errors in velocity estimation will build up quickly and you'll get terrible drift.
In the case of the spatial computing hoop though you know the hoop never gets far away from the user so you can damp the D.C. component of the velocity, work in coordinates relative the user's center of gravity and never notice any drift in the x or y coordinates. (I don't like damping the vertical so much but I think I can live with it.)
