RFID TagRFID: Promise and Peril: "Now suppose that a market research company parks a van outside the supermarket and uses a directional antenna to scan your cart as you wheel it to your car. The grocery store has already done its research, but are your purchases fair game after you've left the store? Or what about an extension of van Eck phreaking (reading electromagnetic emanations at a distance)? Could a high-powered illuminator and a high-gain antenna inventory the contents of your home? It's certainly possible. If you're wearing or carrying anything with an embedded RFID tag, you could conceivably be tracked wherever you go."