Regarding remote controlling the phone when it is in your pocket. I had the idea of trying to use the acceleration sensor to sense "taps" on the phone from the outside of the pocket. It's like giving commands to the phone in Morse code. E.g. ".. .." might mean "previous song", "..." next song. Shaking or rotating is another way, but that is not very convenient when the phone is in the pocket. You might also be able to sense taps on different sides of the phone, as that is basically doing a small rotation in different directions.

I never found the time to play around with is tough. But if someone else would pick up on this idea, I'd love to know about it.