This is not exactly what you're looking for but here's a suggestion. If you get a pair of bluetooth headphones that have avrcp (think that's the acronym), you could fire up your mp3 player (I use mortplayer), hit the power button and place it in a cup holder or in the included leather case, then use your headphones to skip tracks and control volume.
Like I said, this doesn't give you as much control as having the phone on your arm, but it does work great for me when I'm working out. Just make sure that you don't walk away without your phone if you leave it in the cupholder though
