How to Build a laser microphone
Listen to conversations over long distances with a homemade laser listening device. All you'll need is a laser pointer, tripod, old pair of headphones, photocell, a recording device, and the step-by-step instructions in this how-to video. The creator of this video tutorial does not mention the need for sophisticated software. But the principle is quite sound. If you can figure it out, you can eavesdrop and spy on whoever.