This 4-degree of freedom robot arm is made from two Thymio Robots and plenty of lego. The small lego wheels rotates in front of the proximity sensors to measure actual distance traveled. This robot arm was created by: Dr Stéphane Magnenat of EPFL, and Austin Hendrix of Willow Garage Here is the Instructable, containing more pictures.
The people of the Thymio lab at EPFL had a bit of fun with Thymio this year, check out what they did, and have a very merry Christmas yourself!
A drawing robot