Marcus writes in about this interesting interactive light. It isn’t the most compelling video, but I like the idea of the piece. It records the amount of ambient light during the day and plays it back when held. The video is of an older version, but you get the point.
It is a small object (actually half a ping pong ball), interacting with its owner and environment (and being pretty boring without interaction). The object permanently aggregates light samples (i.e. it measures the every second and stores the average every some seconds). If you take it into your hand it notices the raise in temperature and tells you how it experienced the day (i.e. playing back the light levels of the day in time lapse).