As part of the closing down exhibition for The Cornerhouse (before they moved to HOME), we created a machine that would allow people to share their memories of the corner house via twitter/online form. Once a message was submitted, the machine in the Cornerhouse (which consisted of a giant animatronic pencil) would spring into life, moving, flashing and finally printing out the message onto a card. These cards were then displayed around the gallery for people to read.
This was built with Studio Audience and I developed the API which used Silex and MongoDB.