Via taw's blog, a couple of electronic devices to help you manage your electronic environment:
Wave Bubble - a mobile phone jammer. Could be useful for those of us who like to sleep on trains. Unfortunately this is just a design; you have to build it yourself (and apparently it is not easy). Limor Fried, the designer, states: "This design is not for sale or available as a kit and never will be due to FCC regulations". This is obviously why it is small enough hide in a cigarette box.
TV-B-Gone - A universal remote control TV off switch. The homepage includes a video showing it being used to switch off a TV in a shop window. This device does seem to be available commercially here (disguised as a key-fob).