Songs
Years ago, in an IRC channel, I had the idea for taking what was playing on your digital music player of choice on your person. You would want to do this for two reasons: 1. so that you can feel cool and 2. see if anybody gives you respect (or hate) for what you listen to. It would be similar to Last.fm, where you send what you're listening to on a website, except that it would be on your person. Something like a small display that goes around your neck, or hangs off your back.
More inspiration:
http://www.thinkgeek.com/tshirts-apparel/interactive/991e/