I just stumbled upon this guy that has a host of interesting projects going on. The above video describes a method of using any surface as a screen by tracking a projected image onto it in realtime from just one projector. That would be very useful for prototyping various devices with screens. The below video has a really interesting, but maybe not that clear application of RFID tags and projection. The idea is to capture information from RFID tags and project the information from the tags back onto the objects containing the tags.
Check out more videos, and especially the haptic pen