Press one touch sensor or the other inside the casing and watch the hand open and close, push both, and the wrist will rotate. That's all cool and fun, but how does it work? Well, the program determines which touch sensor is pressed or, if they are both being pressed. If its just one, it will rotate the worm gear in one direction or another (seen in the first pic of the U.B.A. without a hand). In each different hand attachment, there are 2 gears, the worm gears slides in between the gears when you place the hand on the turntable. The rotating of the worm gears makes the 2 gears rotate opposite directions, so the "fingers" move together or apart. When both touch sensors are being pressed, the other motor turns. It controls a 8-tooth gear which spins the turn table, making the hand spin around. I would like to give credit to the "One Kit Wonders" book which has a claw in it. My open/close/rotate setup was inspired by that book.
Pic 1: The U.B.A. without a hand
Pic 2: The U.B.A. with a small/thin object grabber
Program: its all commented so you can see how it works
Movie: I will post a video as soon as i can get it to work, LEGO.com isn't really cooperating with my vids.
Here are some more pictures of the U.B.A. Enjoy!