There are two types of people in the world. Those who happily strap an Apple Watch to their wrist every morning, and those who would rather spend the day completely unaware of their heart rate than replace their mechanical watch with a small black rectangle.
For the latter group, HIYD could be rather interesting.
The concept is brilliantly simple. Rather than asking you to replace your watch with a smartwatch, fitness band or smart ring, HIYD sits on the back of the watch you already own. You continue wearing your favourite mechanical timepiece, while the little sensor hidden underneath quietly gets on with monitoring your health.
In other words, you get the data without having to sacrifice the watch.
Your Watch Stays On Your Wrist
HIYD is an ultra slim biometric sensor measuring just 2.7mm thick and 25mm in diameter. It attaches to the caseback of your watch using microsuction, meaning there is no glue, no magnets and, importantly for anyone wearing something expensive, no sticky residue left behind.
The idea is that you simply press HIYD onto the back of your watch, put the watch on your wrist and forget about it.
According to HIYD, the sensor is designed to fit around 95% of watch casebacks, while the company says it is safe to use on polished gold, platinum and glass casebacks.
And because there are no magnets involved, HIYD says it will not interfere with the movement, balance wheel or automatic winding rotor of a mechanical watch.
That last point is rather important. The prospect of attaching anything to the back of a £5,000 mechanical watch is likely to induce mild cardiac distress in some collectors, which is somewhat ironic given that HIYD is supposed to be monitoring your heart rate.
Credit - HIYD
So What Does It Actually Track?
This is where things get interesting.
HIYD isn't simply a glorified step counter. The sensor is designed to monitor heart rate, resting heart rate, heart rate variability, sleep quality, sleep stages, activity, daily steps, calories and recovery.
There is also daily readiness tracking, while HIYD says its app can provide nutrition and calorie information by using your phone's camera to scan food and help track calories and macros.
It also integrates with Apple Health and Google Health, with further integrations reportedly in development.
So while the device itself is deliberately rather boring, the data it feeds into your phone is anything but.
And that's arguably the cleverest part of the whole thing. There is no screen demanding your attention, no buzzing wrist every time you've been sitting down for too long and no temptation to check your steps while pretending to listen to someone explain why their new Submariner is definitely an investment.
The watch remains a watch.
The Perfect Accessory For Watch Collectors?
This is where HIYD makes considerably more sense than it initially appears to.
Watch collectors tend to rotate what they wear. You might spend Monday wearing a Tudor, Tuesday wearing a Grand Seiko, Wednesday wearing an Omega and Friday digging something vintage out of the watch box because you've suddenly remembered you own it.
HIYD is designed to move with you.
Because it attaches using microsuction rather than adhesive, the idea is that you can simply peel it off one watch and attach it to another.
That means your health tracker doesn't dictate what watch you wear that day. Instead, it becomes an invisible accessory to the watch you have already chosen.
And if you don't want to wear your watch while sleeping or exercising, HIYD has thought about that too.
The sensor can be removed from the watch and placed into a softband, allowing you to continue tracking your health while your mechanical watch sits safely on the bedside table.
Four Days Of Battery Life
HIYD claims around four days of continuous tracking from a single charge.
That isn't exactly groundbreaking compared with some fitness trackers, but there is a rather clever solution if you don't want to think about charging.
The optional Battery Band can charge the sensor while you sleep, meaning you can theoretically keep the tracker running continuously without having to remove it for conventional charging. For something designed to disappear into the background, that's a sensible approach.
And There Is No Monthly Subscription
Perhaps the most attractive part of HIYD isn't actually the technology.
It's the lack of a monthly bill.
The company currently lists an early bird launch price of $199, reduced from $299, although the final UK pricing will obviously be something to watch when it launches.
There is no monthly subscription for the health tracking. That's becoming increasingly unusual in the wearable market, where buying the hardware can sometimes feel like merely purchasing the entry ticket before the subscription starts. HIYD's proposition is refreshingly straightforward: buy the sensor and use the data.
The Catch? It's Still A Kickstarter Project
There is one fairly significant caveat.
HIYD isn't yet something you can simply order from Amazon and expect to find on your doorstep next Tuesday.
The company says its second generation sensor is launching on Kickstarter in November, with the first batch expected to ship by Q2 2027 at the latest.
That's worth remembering when looking at all the impressive claims surrounding the device. This isn't a long established product from Garmin, Apple or Samsung. It is a new piece of hardware from a company attempting to carve out an entirely new category of wearable.
The company says it has already successfully launched its first generation product and that the second generation is thinner, more accurate and has improved battery life. Whether it can deliver everything promised is something we'll only really know once the new hardware is in people's hands.
But The Idea Is Brilliant
Regardless of whether HIYD ultimately becomes the next big thing in wearable technology, the thinking behind it is difficult to fault. The problem with smartwatches has never really been the technology. Modern smartwatches are incredibly capable pieces of kit.
The problem for watch enthusiasts is that they are watches. If you have spent years building a collection of mechanical watches, the solution to wanting better health data isn't necessarily to stop wearing them.
HIYD takes the opposite approach. Instead of asking watch collectors to change their habits, it adapts to them. And that is precisely why this could be such an appealing little gadget for the horological community.
You can wear your favourite mechanical watch. You can track your heart rate. You can monitor your sleep. You can keep an eye on recovery and activity. You can track nutrition. You can use your existing health ecosystem. And nobody looking at your wrist has the faintest idea you're doing any of it.
Winding Things Up
HIYD is one of those products that makes you wonder why someone didn't think of it sooner.
For years, the wearable technology industry has essentially told watch enthusiasts that they need to choose. Wear the mechanical watch you love or wear the device that tells you how badly you've slept.
HIYD says you can have both. The 2.7mm sensor hides underneath your watch, uses microsuction to stay in place and collects a surprisingly comprehensive range of health data without turning your wrist into a technology showroom.
There are still plenty of questions to answer. The product is yet to launch, the real world accuracy remains to be tested independently and the final UK pricing will matter. But the concept itself? We like it. Because sometimes the best smartwatch for a watch collector isn't a smartwatch at all.
It's the little bit you can't see underneath your watch.
