A chain or clasp worn at the waist by women with handkerchief, keys, etc., attached, supposed to resemble the chain of keys once worn by medieval chatelaines.
A similar thing in miniature attached to a watchchain.
An item carried on a key ring either as decoration or security.
A passive wireless electronic device that usually uses RFID technology to control access to buildings, containers, computers, etc. by being placed near a detector.
An active wireless electronic device that controls access to buildings or vehicles, such as a remote control for a car door lock.