Flowbio is a London company making a sweat sensor for endurance athletes. The S1 is a small module worn against the skin, clipped to a heart rate strap or threaded onto an arm band, and it is rinsed and reused after every session.

How it works

Sweat carries water and salt out of the body, and the amounts vary enormously between two people of the same weight. Tiny channels draw sweat into the module, where electrochemical sensors read how much fluid passed through and how much sodium it carried. After a workout the app reports total fluid loss, sweat rate, sodium loss and how salty that sweat was.

Key considerations

The S1 tracks no pace, duration or heart rate of its own, so a compatible watch or bike computer has to run alongside it.