KE7GKP:
Arduino is barely capable of tracking a well-contrasted spot on just one camera.
If you need multiple cameras, then you need to aim higher than Arduino.
Not necessarily; while not quite the same as what the OP wants to do, the following was done as an early motion tracking experiment, which was called the "Twinkle Box" - you can download a copy of the paper here at my website:
Ok, how about, i use flex censors all over key points, and then the arduino uses xbee to transfer data to the software to work out, then it projects a biped model?
Processing has some great recognition and motion libraries that use your computers webcam that I've been having fun with. I wrote something real quick just for fun that uses the frame differencing example to set off an alarm if somebody came in the room or anything moved really. I'd look there if using a computer is an option