I thought some would be interested in this unique sensor application using a device known as a Theremin. Mainly used as a musical device, it has applications in other areas as well. This one was used as a way for a robot to sense its environment. The website no longer exists but here is the article with schematics, parts lists, board layouts and instructions.
Pretty cool way of sensing objects.
Here is the manual: ThereminVision-II-manual.pdf
Here is a video of a Theremin being used to play music. Now you know where all that spooky electronic music on the old SciFi movies came from.