Make the invisible visible. The RFBug is a little pink keychain fob with an LED inside that blinks furiously when it's brought into range of radio frequencies between 1MHz and 2.5GHz — your basic data/cellular/cordless phone spectrum. The amazing thing about clipping one of these to your zipper-pull for a couple month is just how much radio there is in the air around us, how much data is passing around, over and through us every second.