wii remote, how does it work
http://planetgamecube.com/forums/messageview.cfm?catid=7&threadid=16110
visiting pixart.com.tw makes it seem like a camera based solution. that actually makes sense because it seems the only way to track cheap and precisely.
howitworks.com ( http://electronics.howstuffworks.com/nintendo-revolution.htm ) says it is just gyros and accelerometers, but i don't believe that at all.