How can I use the camera button to pause/resume mp3?

How can I change camera button functionally and use it (or any other physical button) to pause/resume mp3 in a media player app? It is very important for my, because I want be able to pause/resume mp3 without looking to screen of the phone. Actually my phone (Xperia Mini Pro) has a hardware keyboard with 42 keys, but a few apps use this button as a keyboard shortcut (X-plore is one of few programs that uses hardware keyboard properly).