Blood pressure has long been considered the “holy grail” of PPG-powered wearable technology. Because (so far) you really need an inflatable cuff to measure, or at least calibrate, blood pressure readings, and that’s been difficult to do with a smartwatch alone.
The Huawei Watch D series integrated an armband into the smartwatch itself, while Apple introduced its Hypertension Detection feature, which detects possible hypertension after 30 days of using an Apple Watch, but doesn’t actually provide blood pressure readings. No LED-based device has really cracked 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 other companies, including drone company Skydio, which was eventually acquired by Razr.
Signal is a smart ring with a difference: rather than providing many different measurements like the Oura Ring 5 or the Samsung Galaxy Ring, or using AI assistants like the Google Fitbit Air, it’s designed by “a very smart group of multidisciplinary 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 good,” Moss told me. “So 250 is like insane pressure.”
After her event, Moss attempted to track her blood pressure, but struggled with the wrong sized cuffs and sought a more technical solution. “I went online, bought every type of device that told me they could track my blood pressure, wearable or otherwise, and they are 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 device, not just measure changes from a baseline.”
Working with scientists and engineers at Masimo (the company that sued Apple for violating LED-based heart rate sensing technology), Moss developed the Signal Ring over three years, which can take blood pressure readings on the spot and use a single number — a measurement called “average blood pressure” — to passively track blood pressure throughout the day, broadcasting the information to its companion app via Bluetooth like any other wearable device.
I asked him how a startup could do something that Apple, Oura, Samsung, Google and others had failed to do, and his answer was a matter of specialization.
“That’s our sole purpose as a company,” Moss said. “My co-founders have decades of knowledge about PPG, a cutting-edge treatment…we have a very smart group of multidisciplinary people focused on a single problem.”
Without needing to integrate the sensors needed for other features, such as accelerometers to count steps, the team would have been able to solve the mystery of blood pressure. “It’s not about AI or anything, it’s not that we’re using some sort of magical new technology. We’re putting the best people, the most equipped, to work on it.”
Exciting things in the wearable space, but only real testing will confirm its accuracy compared to conventional blood pressure measurements. Pre-orders for Signal Ring are available now, priced at $399 (around £295 / AU$770) without a subscription (thank goodness!) and are expected to ship in October.
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