Theremin Keyboard

A theremin works by detecting the motion of two capacitors (in the primary case, your hands) within the boundaries of its electromagnetic fields, one of which controls pitch, and the other volume.

For the truly bored, a theremin-like device could be configured so that one hand's motion controls relative position within the alphabet (A-H, I-N, O-S, T-Z, or whatever) and the other selects a letter within that section. This input could then be sent to the computer, so said person could create fine literary masterpieces without ever actually touching anything.

EDIT: This might actually help with typing by people who for one reason or another are unable to use their hands. Elbows, feet, knees, all would work if properly set up.