One day, your FitBit might move on from counting steps and tracking your heart rate to crunching data on something else: your sweat. A group of northern California researchers from the University of California, Berkeley, Stanford University, and the Lawrence Berkeley National Laboratory have developed a wearable sensor that can monitor various components in sweat.

Described in a paper in Nature, the sensor can measure levels of chemicals in sweat including electrolytes like potassium as well as metabolites like lactate (the latter is found in higher concentrations during intense exercise) and can keep track of skin temperature. The flexible, wireless sensor—which sends data to a phone via Bluetooth—can also be incorporated into wrist and headbands.

The table above shows how the make up of sweat changed over time as a study subject biked at an increasingly higher resistance.

In order to test the concept, the researchers had seven test subjects wear the sensors on their head or wrist while working out in the lab. Then, they analyzed their sweat during various workouts, such as cycling up a simulated hill (with higher and higher resistance). They also tested the technology’s ability to monitor dehydration by sending six runners out for 80 minutes while wearing sensors. The found that the sweat sensors were accurately able to detect the signs of dehydration by monitoring sodium and potassium levels, as compared to sweat samples analyzed in the lab.

More research is needed but the technology might be used in the future to study what sweat can tell us about disease.

[h/t: STAT]

All images from Gao et al., Nature (2016)