I am amazed at the future of our children. Somewhere, some kid is going to have a science fair project that teaches him interferometry. This is way cooler than those old books of science fair projects ("grow salt crystals!"). The next generation of kids will be ADD, but have such an amazing breadth of knowledge.

People were talking about this in the 80's. The government line was that it was tried by Spy agencies, but it didn't work.

A couple of links:

http://www.williamson-labs.com/laser-mic.htm

http://lifehacker.com/software/diy/build-a-laser-spy-microph...