Rover uses an MIT "Handy Board" as a controller.  At the upper-right corner of this picture is a Polaroid sonar (salvaged from an old auto-focus camera) that he uses to detect obstacles at a distance.  At the far right is one of his IR reflection sensors, for detecting obstacles nearby.  The chassis was "donated" by a broken radio-controlled truck from Radio Shack.  The radio receiver has been removed, and the original steering motor replaced by a model airplane servo controlled by the Handy Board.