Before I get accused of calling a single solenoid being held by a puppet a robot, let me fill you in on some of the details of how this little guy is actually set up in real life.
The controller board from Highly Liquid allows for MIDI input to trigger solenoids and motors. I am writing a number of apps in Max/MSP to allow for things like randomization of different parts of the playing within a clocked rhythm.
The Robot Drummer's set up actually has 16 channels set up divided between two boxes, one is set up for a 12 volt load the other for 24. So stuff like his eyes of different strikers can be individually controlled.