Sweat-powered fitness devices could rate your pulse, temperature and other vital signs in future, just as long as you work out hard enough.
Researchers at Deakin University, in partnership with Monash and the University of NSW, released a study into the futuristic gadgets on Wednesday, in a development they say could change wearable technology.
And while there is more work to do, the devices could be released within two years.
The peer-reviewed paper into sweat-powered technology was published in Cell Press' Device journal and investigated whether "wearable hydroelectric nanogenerators" could generate enough energy from sweat on a wearer's arm to power a device.
Deakin University research fellow Azadeh Nilghaz said the nanogenerators were powered by sweat moving and evaporating on the wearer's skin.
"They are like a tiny power generation system that harnesses the energy from moving water to create electricity," she said.
"When sweat flows over the device, it creates an electric current strong enough to run small electronics like Fitbits, smartwatches, or other wearable biosensors for real-time health monitoring."
Dr Nilghaz told AAP sensors used to monitor wearers' vital signs would be small at first - between one and two centimetres in size - and would be housed in wool fabric for comfort and technical reasons.
Fitness-tracking gadgets to use this technology would be low-cost, comfortable to wear and widely available.
Despite running on sweat, they would require only modest amounts of the fluid to operate.
"The sweat required to run these devices is very, very small - just one or two drops - because they are microfluidic devices," Dr Nilghaz said.
"We believe if we can continue working on this project, in two years we'll have rule-based nanogenerators that use sweat."
Deakin University researcher Hongli Su, who started the project, said it had taken two years to prove the technology and the research team had a plan to advance it.
"Firstly, we need to improve the energy efficiency," he said.
"Then we'll come back and combine them with biosensors and Bluetooth."
The team will also work to make the devices more durable and washable, so they could be used to track regular exercise.
Wearable technology has been widely adopted in Australia, with research firm Telstye finding more than one in three Aussies owned a smartwatch or fitness tracker.
The devices are currently powered by batteries, however, with many smartwatches lasting up to two days between recharges and some more basic trackers lasting as long as a week.
Australian Associated Press
