Most fitness bands only monitor step counts and heart rate, but a research device developed by scientists at Stanford University and the University of California–Berkeley could change that. They've developed a wearable device that can analyze multiple components of sweat in real time, according to a study published in Nature today. That may have implications for doctors as well as athletes, because the metabolites and electrolytes that the human body secretes in sweat can be used to determine muscle fatigue as well as hydration levels.

"Conventional sweat sensors typically involve patches that are removed for subsequent chemical analysis by separate, non-wearable machines," says John Rogers, a physical chemist at the University of Illinois who wasn't involved in the project. So the device is a big improvement on two fronts: it's a wearable that isn't too clunky and it provides continuous data streams.

The device, which is placed in a headband, can communicate wirelessly to a phone, so the researchers think it could end up in a smartwatch one day. But the scientists don't have a commercial partner yet, and they'll probably have to scale the whole thing down before they move ahead with their plans. Still, the study suggests that the stuff that's secreted from sweat glands in times of stress could one day help humans design better workouts. Check out the video above to learn more.

Video by Miriam Nielsen and Kimberly Mas.