Invention: Automatic Toilet Paper Dispenser

I was struggling with the toilet paper roll this morning, and I started to wonder why there isn't an automatic toilet paper dispenser that would automatically feed out and cut just the right amount.

For cleanliness, you'd want it to be motion activated, but you'd need a backup system so it wouldn't accidentally feed paper when it wasn't wanted. So, I was thinking sound would be a good backup. You could set it up so that if you tapped your foot and waved your hand under it... Wait... Never mind.