Rock is a rock with a personality. It responds to various things, like poking and pressing on it, stroking, hand position etc. It responds by making noises somewhat like a real pet. On the technical side, it uses a webcam to make a rock into a multi-touch pressure sensitive surface. There is something a bit magical about the rock interface, it feels really good, and it offers such a vast range of expressive input that the rock keeps getting more and more interesting. The noises it makes seem to be really successful at drawing people in and getting them playing with it.
The rock was exhibited at the reActor2 Digital Live Art Conference, and won a prize for best paper (best rock?). The finger pressure sensing technology is the subject of a paper at Pervasive 2008, and a New Scientist online article.
Look at the Rock project to see publications and performances relating to the rock.