Pryme Vessyl
Mark One's Pryme Vessyl
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Water is our simplest nutrient. It requires no more preparation than turning on a tap. We know when we need to drink it because we feel thirsty. Fully functioning adults tend not to forget to drink enough water to survive.

Yet companies old and new want to convince us that humanity has a drinking problem. New “smart cups” from Thermos and San Francisco-based start-up Mark One use an array of sensors that beam users’ real-time data about water consumption to a smartphone app. But does such a simple act as drinking really need all this tech?

Being well hydrated can make us feel more alert and focused, as well as boosting our immune system. The apocryphal advice of eight glasses of water a day is actually a little less than the 2.7 litres recommended for women and 3.7l for men by the US Institute of Medicine. But, as the institute concluded: “The vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide.”

Pryme time
Nonetheless, Mark One believes its algorithm can do better than humans.

When setting up its $100 smart cup, called Pryme Vessyl, I told the app my age, weight, height and sleeping hours. As an optional extra, I also gave it access to my iPhone’s activity and workout data, collected through fitness trackers such as Apple Watch or Jawbone’s UP.

Pryme Vessyl crunches this data in the cloud to create what it says is a more personalised and dynamic hydration target. But rather than tally this in regular litres or ounces, it uses a curious metric of its own invention, also called Pryme.

This obscurely calculated score is tallied up on the app and also appears as a thin strip of white light on the outside of the cup. The line lights up when you tilt the cup, ending in a blue dot if it judges you are sufficiently hydrated at that moment.

This light is an elegant touch on the otherwise minimalist white cup, which at least is not too brash about its “smarts”. The white matt plastic exterior is pleasant to hold and comfortable regardless of whether the cup contains iced water or hot tea.

However, the glass interior makes the cup pretty heavy, while its “splashproof” sliding cap does not prevent drips and leaks. This makes it unsuitable for use during vigorous exercise, when hydration monitoring might be most useful.

My main incentive for maintaining Pryme became to silence the constant nag of push notifications that arrived whenever I was short of my goal. My phone often pinged when I had just taken a sip with urges to take another, to “get you to the next level”.

Smart Lid Thermos 2.0
Thermos Smart Lid

Mark One has raised millions of dollars in venture capital to develop a more ambitious cup that claims to track the type and brand of drink inside, including calorie and caffeine content.

However, that product has had more than a year of delays because of problems with sensor reliability, with no shipping date in sight. In the past few months, the company has suffered the departure of its heads of health, design and software, as well as founder and chief executive Justin Lee.

Thermos 2.0
Thermos’s $60 Smart Lid device is more utilitarian. Its app simply tracks how much water is in the bottle (in case you can’t see through its transparent side), its temperature (in case holding the cup was insufficiently precise), how much water you have consumed and — for fans of pointless statistics — how many minutes you have spent drinking and how many sips you have taken that day. You can set your own water consumption goal (in plain old litres), with a bar tracking your progress, and the total amount drunk can also sync to Fitbit’s app.

The plastic bottle and its lid are light and watertight, which at least makes it more practical than the Pryme. But I found the data transfer unreliable. On one occasion, it told me I had spent 1,143 minutes taking one sip, to consume 7ml of water.

The human body comes with robust hydration sensors — based on input and output — pre-installed at no cost to the user. We may all benefit from the occasional reminder to drink more water, but there are far cheaper ways to do that than these devices.

Amid the ongoing “internet of things” hype, the argument that a cup or bottle must be “smart” just does not hold water.

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