iOS 5 beta 3 enables a new “Assistive Touch” option in the accessibility settings menu. Assistive Touch allows users to tap a corner to bring up an overlay with various functions such as shake, volume up/down, rotate screen, lock, swipe, pinch, and more. This feature is intended to assist users who are unable to perform these actions themselves, but can also be used as a replacement for hardware buttons (which are known to wear and break over time). Custom gestures can also be recorded and saved for automatic playback, making tricky gestures easy to recall.
iOS 5 beta 3 is available for developers, and will be released to the public this Fall.