Safe-t Mate SM-004B Personal Fall Monitor.  Brand new, in the box, comes with 9V battery.

We’ve redesigned our popular fall monitor. Our goal was to maintain the rugged durability while adding valuable features. The simple and reliable switching mechanism uses a surface mounted magnet that releases in any direction. We added a low battery warning LED and low power consumption circuitry for extended battery life. The unit features a soft silicone jacket for drop protection, integrated upholstery clip and 95 db pulsing horn. The cord assembly is adjustable from 18” – 32” for a variety of applications. 9V battery included. Great item for alerting when a person tries to get up out of a wheelchair or bed.