A person who goes by the moniker The Herb Puffer on Reddit snapped this photo of a Hershey Chocolate Bar bearing Riteaid's latest shoplifting deterrent technology – an RFID sticker with a printed warning.
The website Explain That Stuff explains how that stuff works:
If you walk through the doorway without paying for something, the radio waves from the transmitter (hidden in on one of the door gates) are picked up by the coiled metal antenna in the label. This generates a tiny electrical current that makes the label transmit a new radio signal of its own at a very specific frequency. The receiver (hidden in the other door gate) picks up the radio signal that the tag transmits and sounds the alarm. Why doesn't the alarm sound when you pay for something? You may have noticed that the checkout assistant passes your item over or through a deactivating device (sometimes it's incorporated into the ordinary barcode scanning mechanism, and sometimes it's completely separate). This destroys or deactivates the electronic components in the RF label so they no longer pick up or transmit a signal when you walk through the gates—and the alarm does not sound.