Let's see...... Someone mentioned a back-up "beeper". Great idea, especially at the grocery store on "Geriatric Wednesdays".
Ray showed the flashing light, also a good idea for Geriatric Wednesdays as a bunch of them are hard of hearing and/or haven't changed the batteries in their hearing aides in weeks.... "WHAT!?!?!?"
Chris! MAYBE........ You could do BOTH!