Spyguard endorsed by British government to reduce RF emission of wireless networks: The window film and a similar paint reportedly turn rooms into Faraday cages without all the tedious insertion of a metal mesh. But MI5 gets to monitor who purchases the materials.
The group selling it claims it was developed by the NSA and that they have exclusive rights. Sounds a little James Bond-ish. Why would the NSA allow such an item to be sold overseas? I checked, and I'm wrong: they have a list of technologies available for license. (Hey, what happens when you link to the NSA?)