Wheelchair Controlled by Thought

A motorised wheelchair that moves when the operator thinks of particular words has been demonstrated by a US company (see video, right). The wheelchair works by intercepting signals sent from their brain to their voice box, even when no sound is actually produced.

This is pretty nifty and the video is a nice demo but I could not help but wonder what would happen if an ADD wheelchair user got distracted while in mid motion --- humorous or frightening?