4-Degree of Freedom Thymio Lego Arm with LEGO

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.