Canon semi-pro and pro cameras used to have Eye-Control autofocus. This system allowed for picking one of the points of the autofocus system simply by looking at it though the viewfinder. An infrared transmitter and receiver mounted around the eyepiece monitored the position of the iris, thus "knowing" where the photographer was looking and focusing on that point.

It worked well for me, and I really miss that system. Does anyone else miss it? Do you know why it's not offered on today's cameras anymore? Will Canon ever bring it back?