Mechanically, there's a lot going on under the hood. Take a look at gearhead motors and "spin rings".

Each BlinkM is attached to a long, flat cable, which in turn is wrapped around a custom-built reel. That reel is rotated clockwise, or anti-clockwise, by a small DC gearhead motor (“gearhead” simply means that the motor includes a set of gears to slow down the rotation of the axle, while also greatly increasing torque).

The artist added a high-reliability microswitch to each unit. This switch is triggered when the software occasionally recalibrates the position of the light pendant.

The cable needs to maintain a permanant electrical connection to the rest of the circuit. Ordinarily, that would present problems because the cable would get "bunched up" with all the winding and unwinding. The artist solves this problem by using a spin ring. This special device allows one end of the ring to turn in either direction, and is static on the opposite end, which attaches to the main circuit.