Some Ideas:


Using an etch-a-sketch is hard, hooking it up to a mouse might seem harder, but in the end, likely more appropriate and accurate. here comes the electr-o-sketch--hack a mouse to control and draw on the classic and ever present etch-a-sketch.



It used ultrasonic sensors to determine orientation and could detect four different positions per finger. The finger's resistance varies depending on how much it is bent, so Brandon used an LM339 comparator to determine the mouse clicks. For the actual mouse interface he used the guts of a Gyration mouse.