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Heart disease is the leading cause of death among firefighters, in large part because of their extended exposure to high-heat situations, a problem that also affects industrial workers and members of the military. SlateSafety aims to solve this problem with the BioTrac Band ($495), a wearable tracking device that watches for signs of heat stress. Worn on the arm, the device measures each user’s heart rate, core body temperature and exertion, pinging a cloud-based platform to alert commanders and colleagues when those measures hit unsafe levels. Since its inception, the company has been awarded $1 million by the National Science Foundation and has received three contracts from the Department of Defense; the device is now used by 35 fire departments and the U.S. Army, Navy and Air Force. —Abhishyant Kidangoor

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