A couple of us from the London Hackspace got invited to build and demo a machine for BBC Click ( on BBC world services). We threw together a machine that listens for tweets, dispenses a ball into a holding area and then at the end of the show fires them into the audience.
Heres a few pics
Heres the complete setup
A nice closeup of the Ball Holding area (thrown together in half an hour with a glue-gun)
The large-ball accellerator
And sure enough we had more tweets than balls
Tom Scott produced a nice video of the whole setup:
The show is available on BBC iPlayer here