Not drinking sufficient water is a common problem. A 2023 study suggested, external that one in four UK adults aged 65 or older were dehydrated, due to not drinking sufficient fluids.

And a 2018 study by Flouris, external and colleagues assessed hydration levels in 139 workers around Europe. They found that 70% were dehydrated to a level that could negatively affect their thinking and control of their movements.

Purveyors of hydration tech say their products can help. Years ago, gadgets such as the Apple Watch and Fitbit made step-counting popular, says Roozbeh Ghaffari, co-founder and chief executive of US-based Epicore Biosystems. But why stop there? "Sweat has been the next chapter," he asserts.

His company is one of several that makes sweat-analysing devices. In Epicore Biosystems' case, that includes single-use sticky patches and sleeve-like wearables, which track the flow rate of sweat as it emerges from your skin, the sweat's sodium (salt) content, and skin temperature, among other metrics.

A new armband and app combo also offer to evaluate your "hydration readiness" based on "real-time sweat data". The idea is to avoid dehydration creeping up on you.

"With this new generation of our wearables, we could figure out what type of risk profile you have based on your sweat score," says Ghaffari.

Some of Epicore Biosystems' devices vibrate gently when they calculate that it is time for you to take a swig of fluid, to avoid becoming dehydrated.

The company says its devices are used by athletes but also workers on building sites, at oil and gas facilities, and on the ground at airports, where exposure to high temperatures and physical exertion are common features of the job.

Flouris is a little sceptical of sweat-sensing.

Referring to various unnamed devices that analyse sweat, which he has evaluated in the lab, he says, "Most of these products that we've tested do not show the level of accuracy that you would expect." The results of his experiments are as-yet unpublished.

Sweat sensors, Flouris suggests, work best when worn during long bouts of physical activity – such as a marathon. But they struggle when the exertion is more varied and intermittent. Think a footballer switching from walking to suddenly running very quickly.

In response, Ghaffari says he and his colleagues have published peer-reviewed papers, external on the accuracy of Epicore Biosystems' gadgets.

He acknowledges that analysing sweat loss over short intervals up to 20 minutes long "can be challenging" but says his company's products appear effective for 30-minute, or longer, workouts.

Perhaps the most common hydration-focused products available are the smart water bottles that remind you to take a sip throughout the day.

"We try to make it fun," says Cem Bakiş, head of business development at WaterH, which has a glowing ring that blinks in order to prompt its owner to take a drink. "You can add friends, you can earn points."

Some smart water bottles work by estimating the weight of liquid in them, and how that changes over time as the drink inside is consumed. But WaterH takes a different approach.

Sensors detect when the water bottle is tipped at an angle, and also the flow rate of fluid as it leaves the vessel. The water bottle will immediately recognise when you've had a sufficient quantity of liquid, stresses Bakiş.

I point out that, while some reviews online are positive, other comments criticise the accuracy of these measurements. This is often an issue with how the device is calibrated, and easily rectified, responds Bakiş.

If you don't want to take instructions in hydration from a water bottle, though, you always have the option of asking your toilet how things are going.

Vivoo makes a urine-analysing gizmo that sits on the rim of a toilet bowl, promising to help you understand your hydration "like never before".

The device uses optical sensors to work out your "urine specific gravity" – a measure of urine's density compared to clean water. The denser it is, the more dehydrated you are, generally. Small print on Vivoo's website emphasises that its products are not intended to provide medical diagnoses.

Urine-based measurements are used to evaluate hydration in scientific studies, says Flouris. Though he notes that there can be some delay between a person entering a dehydrated state, and this becoming detectable in their urine.

Hydration-monitoring gadgets are "interesting", says Tamara Hew-Butler at Wayne State University – though she questions whether they might raise people's anxiety about their health.

More metrics, reminders and goal-setting are not necessarily what everyone needs. "It's added some information – but it's also, I think, added a bit of an emotional burden," she says.

Bakiş says the WaterH smart bottle is intended to help people "build a habit" rather than stress them out.

A spokeswoman for Vivoo acknowledges the concern that frequent health-tracking could become anxiety-inducing. "Vivoo's smart toilet technology is designed around passive, routine-based testing," she says. "Users do not need to take additional steps or repeatedly check an app throughout the day."

Hew-Butler says hydration tech could have some special uses. For example, sweat monitors that alert a coach to one or two members of a team becoming dehydrated. Those individuals might not otherwise speak up independently because "they don't want to appear weak", suggests Hew-Butler.

"What technology does is it gives us this immediate result," she says. Ultimately, avoiding dehydration, and also over-hydration are important – but the human body is more adaptable than we sometimes assume, adds Hew-Butler. "There is a little bit more of a range of safety there."