Gus! Dwell Cursor
Gus! Dwell Cursor provides a practical method of activating mouse button clicks (click, double click etc.) for users who have difficulty accessing standard mouse buttons, or who use one of the new "head pointing devices" that remotely control the cursor. Move the cursor over the item you want to "click", and Gus! Dwell Cursor automatically does the mouse clicking for you!
More information: http://www.synapseadaptive.com/augcom/gus/Cursor.htm