Get the full scoop at exothermia.net/monkeys_and_robots/2009/04/27/cloudmirror/
The CLOUD MIRROR is an interactive augmented reality art installation by Eric Gradman of Monkeys & Robots. Live video captured by a camera is projected on the wall behind the camera. The CLOUD MIRROR software alters the images on the way to the screen. It tracks faces from frame to frame and also examines each frame for 2D barcodes printed on attendee badges.
The CLOUD MIRROR then augments each frame, adding a thought bubble to each face in the projected image. The contents of that thought bubble are selected from a set of "tags" associated with that person. Tags come from various sources, including Facebook, Twitter, and SMS data.