Meet mROBerTO: a tiny millirobot designed for swam robotics with an ARM processor, Bluetooth 4.0, and ANT. It has a modular design with 4 parts. It was built mainly using off-the-shelf components. The robot has IR emitters and sensors to determine when other robots are near, up to 150mm. It has 2 motors in the back to move.
These robots can work as a group autonomously in a decentralized fashion. More info is available here.