Flock cameras—solar-powered, automated license plate readers, weighing less than 3 pounds and designed to be unobtrusive—can be found on 80,000 street corners throughout the country. The company behind the cameras built an $8.3 billion business empowering officers to track people’s movements.

Nationwide, Flock cameras log billions of license plates each month. And now dozens of reports are emerging of police using the cameras not to solve crimes, but to stalk their partners and exes.