As an inventor, I noticed this thread and couldn't help commenting. The logic seems compelling but will need a bit of development. Take a simple artist's manniquin. Rigid wooden bones plus head connected to ball joints. If each joint is a ball then each ball might be a trackball, covered with dots as per the MS trackballs and a sensor in each end of the joint reports on its position on the ball as it is moved. Move the figure freely and the sensors report just like mice. The mouse driver technology exists, as does the driver software. What doesn't exist is the ability to collect data from (quick guess!) 30 'mice' at once on a single PC. All optical and no gears. One trivial problem is making the balls move freely enough to allow joints to be moved by hand but rigid enough so that the figure doesn't fall limply all over the place. Additional friction is needed per joint. Make a nice project for someone and trackballs are always on offer in big stores in the bargain bins since so few ppl use them... Bit big though (1 inch diam?) Optical tech is probably too heavily patent protected too but even so worth a try I'd have thought. Just an idea! Let me know if anyone wants to try it.