This is a really cool theory. I don't know if in the end it will be true or not, but I thought I'd throw my two cents in. What if instead of an IR, UV, Proxy or any other light sensor, these seems functioned more like the existing technology in an iPod click wheel. Quoted from HowStuffWorks:
"At its most basic, a capacitive-sensing system works like this: The system controller supplies an electrical current to the grid. The metal channels that form the grid are conductors -- they conduct electricity. When another conductor -- say, your finger -- gets close to the grid, the current wants to flow to your finger to complete the circuit. But there's a piece of nonconductive plastic in the way -- the Click Wheel cover. So the charge builds up at the point of the grid that's closest to your finger. This build-up of an electrical charge between two conductors is called capacitance. The closer the two conductors are without touching, the greater the capacitance."
Perhaps they would work more like the description above? You touch one or more of these spots with your finger to complete the curcuit and activate the intended function. Granted, it poses some of the same potential problems as the light sensor theories, but at least you eliminate the need for light all together and it shouldn't be a horribly power draining system.
