The rig was created and programmed by Sarah Angliss. It plays many tunes, but in this video we are hearing a rendition of Troika, from Prokofiev's Lieutenant Kije (duh).
Sarah's provided some technical details:
The bells are being played by wooden balls, spring-mounted on servo-controlled beaters, running off a LynxMotion SSC-32 board, receiving serial signals from a Max/MSP patch (which is interpreting a midi file). These bells have been recycled from Swinging London, my 2006 installation for the Overture Weekend at the South Bank, London. Here they've been mounted on a stainless steel shop fitting, reclaimed from the back yard of Moore's of Dunstable.
And all that is powered by a Mac laptop (MacBook? Pro? She doesn't say). [YouTube — Thanks, Sarah!]