Foggy memory, but either the CIA or KGB embedded tiny prisms in embassy window(s) so it was easy to capture the reflection. Without the prism it seems like this would be a real pain.

Here's another awesome way to pick up sound covertly: http://www.nsa.gov/museum/museu00029.cfm

I'd love to see some instructions how to do that easily. I'd love to try it.

That is deeply awesome. Only of use if you want to listen to a window that you can hit almost perfectly straight on though. They have the two components at quite an angle, that wouldn't be practical if you were trying to be discreet...

If I remember right from high school physics class, hitting it at a greater angle will get you a better reflection, and hence better sound quality.

Time to buy an IR laser to really fool all but the most observant.

I suppose aiming might be hard, but getting a camera that sees low res IR shouldn't be too hard.

Some IR lasers http://www.nvginc.com/irlasmod.htm

Such a clever hack.