2 of 16Image
Activator is one of the most popular jailbreak iPhone, iPad, and iPod touch applications available. It allows you to assign gestures and reassign hardware buttons to launch applications or perform certain functions.
With it, you can assign any hardware key on your iPhone, such as the home button, to launch an application on a sequence, such as a double-press or a short-hold press. You can even assign your volume up- and down-buttons to adjust how loud your music is -- while short-holding the up-key to skip to the next track, and short-holding the down-key to jump to the previous track.
Compatible with: iOS 5, 5.0.1 (and 5.1, though not yet officially supported, it works.)