Part of the iPhone UIKit framework.

Little is known about the elusive yet omnipresent GSEvent, though researchers believe the GS stands for “GraphicsServices”. One very useful function is

CGRect GSEventGetLocationInWindow(GSEvent* event);

Other known functions are:

int GSEventIsChordingHandEvent(GSEvent *ev);

int GSEventGetClickCount(GSEvent *ev);

Maybe worth looking at:

GSEventGetDeltaX

GSEventGetDeltaY

GSEventVibrateForDuration