Quote:
Wi-Fi-Blocking Wallpaper Protects Your Web Fortress by Keeping Neighbors Out
Scientists from the institut polytechnique Grenoble INP and the Centre Technique du Papier have developed a novel new product so gratuitous, it almost seems necessary: a silver-crystal coated wallpaper that can block neighbors from freeloading off your Wi-Fi network. The silver crystals are arranged in such a way that they are able to block certain wireless frequencies, not least of which is the same frequency as a WiFI router.
There is more at the link posted below. Enjoy :)