Using Twitter4J on a host PC and a little webserver magic the code for this could be accomplished in less than an hour.
However you need to be aware that you can't query Twitter more than twice a minute, so if you get a lot of activity the pump will simply activate once every 30 seconds like clockwork. More cunning programmers would process the times of multiple tweets received and spread out the events over a 30 or 60 second window for a realtime effect, though delayed slightly.