Velcroman1 writes "Retailers are experimenting with a variety of new ways to track you, so that when you pick up a shirt, you might get a message about the matching shorts. Or pick up golf shoes at a sports store and you see a discount for a new set of clubs. New technologies like magnetic field detection, Bluetooth Low Energy, sonic pulses, and even transmissions from the in-store lights can tell when you enter a store, where you go, and how you shop. Just last year, tracking was only accurate within 100 feet. Starting this year, they can track within a few feet. ByteLight makes the lighting tech, which transmits a unique signal that the camera in your phone can read. The store can then track your location within about 3 feet — and it's already in use at the Museum of Science in Boston."