Easystroke is a gesture-recognition application for X11.

Gestures or strokes are movements that you make with you mouse (or your pen, 
finger etc.) while holding down a specific mouse button.  Easystroke will 
execute certain actions if it recognizes the stroke; currently easystroke 
can emulate key presses, execute shell commands, hold down modifiers and 
emulate a scroll wheel.

The program was designed with Tablet PCs in mind and can be used effectively 
even without access to a keyboard.  Easystroke tries to provide an intuitive 
and efficient user interface while being highly configurable and offering 
many advanced features.

This requires help2man, boost, and gtkmm.