The servo is a controllable motor that can swing back and forth or be turned to a specific position. Attach a flag to the arm to make it wave back and forth. There are even a few littleBits accessories made just for the servo (like the mechanical arm).

The servo has 2 modes. In TURN mode the input from other Bits determines the position of the hub – try using a dimmer to set the angle you want. In SWING mode the servo will move back and forth on its own like a pair of windshield wipers – the input signal controls the speed of the swing. The servos range of motion is about 110 degrees.