Blood pressure has long been considered the “holy grail” of PPG-powered wearable technology. Because (until now) you really need an inflatable cuff to measure or at least calibrate blood pressure readings, and that’s been hard to do with a smartwatch alone.
The Huawei Watch D series incorporated a cuff into the smartwatch itself, while Apple has introduced its Hypertension Detection feature, which earmarks possible hypertension after 30 days of wearing an Apple Watch, but doesn’t actually provide blood pressure readings. No LED-based device has really been able to crack it. Until now, apparently.
The Signal Ring is the brainchild of Tom Moss, a former head of Android at Google who has founded several companies since leaving Google and co-founded several others, including the drone company Skydio, which was eventually bought by Razr.
Signal is a smart ring with a difference: Instead of providing many different metrics like the Oura Ring 5 or the Samsung Galaxy Ring, or using AI assistants like the Google Fitbit Air, it was designed by “a very smart group of multi-disciplined people focused on a single problem” – and that problem is blood pressure, which Moss was inspired to tackle after a cardiac event, a ‘hypertensive emergency’.
“My blood pressure was 250. If you can imagine, for blood pressure, 120 [over 80] is healthy and fine,” Moss told me. “So 250 is like an insane amount of pressure.”
After his incident, Moss tried to track his blood pressure, but had difficulty with wrong-sized cuffs and sought a more technical solution. “I went online, I bought all kinds of devices that told me they could track my blood pressure, wearable or otherwise, and they’re all garbage.”
Some watches, such as the Samsung Galaxy Watch series, use an initial blood pressure cuff reading to calibrate, then estimate your blood pressure by looking at other vital signs between calibrations. But Moss found this approach frustrating and inaccurate. “We needed a way to measure blood pressure from a wearable, not just measure changes from a baseline.”
Working with scientists and engineers from Masimo (the company that sued Apple for infringement of LED-based heart rate sensor technology), Moss developed the Signal Ring over three years, which can take blood pressure readings on the spot and use a single number – a metric called ‘mean arterial pressure’ – to passively track blood pressure throughout the day, as well as its Bluetooth companion app information can be broadcast over Bluetooth.
I asked him how a startup could do something that Apple, Oura, Samsung, Google and others had failed to do, and his answer was specialized.
“This is our sole focus as a company,” Moss said. “My co-founders have decades of knowledge about PPG, state-of-the-art treatment… we have a very smart group of multidisciplinary people focused on a single problem.”
Without having to cram in sensors required for other functions, such as accelerometers to count steps, the team was reportedly able to crack the blood pressure mystery. “It’s not artificial intelligence or anything, it’s not that we’re using some kind of new, magical technology. We’re putting the best people, the most equipped, to work on it.”
Exciting stuff in the wearables space, but only real testing will confirm its accuracy compared to conventional blood pressure readings. Pre-orders for the Signal Ring are available now for $399 (around £295 / AU$770) without a subscription (thank goodness!) and are likely to ship in October.
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