To catch a thief may stop a heart
Devices to nab shoplifters can interfere with the functioning of pacemakers and implantable cardioverter-defibrillators.
The exits of most stores these days are guarded even when there's no security guard in sight. Doors are monitored by "electronic article surveillance" systems that use radio or electromagnetic waves to detect whether tiny sensors affixed to the merchandise have been deactivated. If they haven't, an alarm goes off. Often these systems are in plain view: two pedestals — one serving as a transmitter, the other as the receiver — form a little checkpoint that you walk through as you leave the store. They're so common now that we hardly notice them.