A2DP uses will know how convenient it is to control our music from your headset. HTC sells a remote which allows one to do this from your headset, but that is an added cost, and does not work with all HTC devices like the Touch HD.
Daniel1515 decided to do something about the situation by developing an app which allows a user to assign a function to a double tap of the phone answer button on the bundled HTC headset. Daniel intends to extend this functionality further, to add support for a long press and possibly other signals.
At present one can only choose from Back, Next song and play/pause, but this should be extended soon.
The app should support most current gen HTC devices using HTC AudioManager, but has been mainly tested on the HTC Touch Pro.
The app is open source, so if you have a good idea of improved functionality you can have a go at it yourself.
Read more and download the cab here.