Sensors can read your sweat and predict overheating. Here’s why privacy advocates care

On a hot summer day in Oak Ridge, Tennessee, dozens of men removed pipes, asbestos and hazardous waste while working to decontaminate a nuclear facility and prepare it for demolition.

Dressed in head-to-toe coveralls and fitted with respirators, the crew members toiling in a building without power had no obvious respite from the heat. Instead, they wore armbands that recorded their heart rates, movements and exertion levels for signs of heat stress.

Stephanie Miller, a safety and...