Football players are prone to heat strokes due to the gear and helmets they wear, compounded by working out in off-season training facilities in places like Florida and Arizona. While training in 2001, Minnesota Vikings lineman Korey Stringer died due to heat stroke. To allow teams to monitor the players’ individual temperatures, Hothead Technologies out of Atlanta, Georgia has developed sensors that can be built into helmets to provide live wireless updates.
From Popular Science:
The Heat Observation Technology (HOT) system uses an electric thermometer called a thermistor, a spoon-size device made of metals whose electrical resistance vary with temperature. Inserted under the padding of a standard helmet, the thermistor measures the temperature in the player’s temporal artery and uses a built-in radio to transmit temperatures between 99.9° and 110°F — heat illness typically sets in around 104° — every 10 seconds to a PDA monitored by a coach or trainer on the sidelines.