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World Cup water breaks highlight growth of hydration-focused products.

Some businesses have identified a gap in the market for products that monitor how hydrated people are.

Climate change means more frequent heatwaves and public health campaigns that urge people to drink more fluids.

US company Epicore Biosystems makes wearable sweat-sensors, including sticky patches and armbands, which measure the flow rate and salt content of a wearer's sweat.

The company's target market includes athletes, but also outdoor workers, such as those on building sites or at airports, who are often exposed to high temperatures as part of their job.

Turkey-based WaterH sells a smart water bottle that tracks how quickly liquid leaves the bottle. It uses a reward-based app, to encourage repeat use and build customer loyalty.

Some scientists are sceptical about the precision of these products. Inaccurate results could damage consumer trust and brand reputation.

There are also ethical concerns that constant health-tracking could increase customers' anxiety rather than improve their wellbeing.