Amid rising concerns over post-traumatic stress disorder (PTSD) and other mental illnesses, two MIT startups are developing wrist-worn sensors that can detect physiological changes—including perspiration and elevated temperature—that may signal the onset of events like anxiety attacks.

The data collected by these devices can be fed into an algorithm that aims to learn what triggers anxiety, or when people may be about to engage in a risky behavior. One goal is to head off destructive behavior, from drug abuse to suicide and violent outbursts, and to help with treatment.

Although the technology is still experimental and the devices are used mainly in medical research, they herald the appearance of consumer versions and associated apps that let people monitor their mood and stress levels. Other emerging technologies aim to detect emotion using subtle cues from how people use smartphones (see “A Smartphone That Knows You’re Angry”).

The newest of these startups, Boston-based Neumitra, emerged from stealth mode earlier this year with a device that can measure proxies for excitement or stress, including increased motion, increased skin conductance from perspiration, and elevated skin temperature. The device, called bandu, sends readings to the wearer’s smartphone, which records them for later analysis. The device also includes a display that can be customized to suggest, say, that you take your medication, call a loved one, or listen to a song.