Team BUTIÃ from Uruguay has been working on an XO robotics project for over a year. They showed off their line-following XO-robot, butiabot, in Montevideo this weekend. An XO running TurtleArt code hooked up to a mobile robotic platform followed a dark line along the ground.
They have posted some details of their prototypes online.
This reminds me of the XO hack to control a Roomba over the Net, but cooler, with Turtle Art and a realtime-hackable control program.