For one of my applications, I need a passive tag to respond to a given signal from a reader by emitting a sound.
Some RFID chips have input/output ports that allow them to send information or signals to a device. As such, it is possible to add a device to a passive tag that will make it beep under certain conditions, or when it receives a command from a reader, but I am unaware of any tag currently on the market that offers this functionality. If any of our readers have information about a commercially available tag with this functionality, they are invited to post it below.
—Mark Roberti, Founder and Editor, RFID Journal