I'm not a hardware guy, so does this mean that almost all USB devices can be turned into USB HID devices? Or is it something in the MP3 player?
edit: nevermind, i read http://www.hak5.org/forums/index.php?showtopic=16756
This is fantastic. The only problems I see with this is 1) most mp3 players that support Rockbox are bulkier than the tiny teensy, and 2) that you'll have to carry around the cable.