For those of you that speak german, this is an interesting link:
Basically, the german government wants to purchase a device to find bugs that
communicate with the outer world via infrared/optical means.
For me as somebody totally clueless about surveillance/eavesdropping devices,
I am intrigued by the idea of using infrared for communication with the outside
world: One the one hand, since the beam can be so highly direction, I'd assume
it is going to be extremely hard to detect it (aside from putting lots of smoke/
particles into the air), and can also be minituarized significantly (as one doesn't
need much of an antenna to emit the waves).