The Smart Ring That Promises Cuffless Blood Pressure Apple and Oura Won't Claim": Here is the contradiction most people miss: the smartest thing the founder of the Signal Ring has said about his own product is that most people shouldn't buy it.
Tom Moss will tell you the ring exists to save lives. He'll also tell younger, healthy buyers to "just buy an Oura or an Apple Watch." Both statements are true. The gap between them is where you should be reading carefully.
Start with the scene that built the company, because it earns your attention honestly. A few years ago Moss — a burly tech executive with a résumé that runs through the early Android team, Nextbit, Razer, and drone maker Skydio — was rushed to the hospital with a systolic blood pressure of 250 mmHg. The upper limit for a healthy reading is 120.
He survived. What haunted him afterward wasn't the emergency; it was the ignorance. He couldn't see what his blood pressure was doing, or what moved it — a workout, a coffee, a bad day. So he teamed up with two engineers from pulse-sensor company Masimo and, per Engadget, spent three years building a ring that would answer the question he couldn't.
That's a genuinely good reason to build something. It does not automatically make the thing trustworthy.
Here's what the $399 Signal Ring does that Apple and Oura won't: it shows you a number. Actual systolic and diastolic readings, from your finger, with no arm cuff for setup and — the real headline — no recurring calibration. Preorders opened July 16; shipping starts in October. No subscription.
The calibration-free claim is the entire pitch. Rival devices from Samsung and Whoop can produce blood pressure numbers, but they need a cuff to calibrate first, and because your arteries stiffen and change over time, they need recalibrating to stay honest. Moss dismissed such drifting readings as, in Engadget's words, "less than useless." His fix is a sensor that, per Vital Signals, reads blood flow four to five times faster than competitors', feeding a custom algorithm.
And the number is exactly the problem.
A number invites action. You see 145 and you worry; you see 118 and you relax; somewhere along the way you tell your doctor, or worse, you adjust how you feel about the medication you're on. The digit isn't just data — it's an instruction people give themselves.
The digit isn't just data — it's an instruction people give themselves. A number invites action, and that feeling, not the sensor, is the product's most dangerous feature.
Which is why it matters that a few readings were simply wrong. In Bloomberg's own hands-on demo, some measurements came back inaccurate. Vital Signals reportedly blamed ring fit — a meaningful admission for hardware whose entire accuracy claim rests on consistent skin contact against your finger.
The FDA has already named this exact hazard. It warns that relying on unauthorized blood pressure wearables can delay treatment or prompt an inappropriate medication change. That's not a hypothetical about bad UX. That's the agency describing how a wrong number on your finger hurts you.
And the broader science hasn't caught up to the marketing. As recently as December 2025, the American Heart Association recommended against cuffless blood pressure tools for diagnosis or treatment, because they simply aren't accurate enough yet. The Signal Ring is a cuffless tool. It is trying to challenge that verdict, but it hasn't overturned it.
Now, the part everyone treats as timidity but is actually strategy: why do Apple and Oura refuse to show you a digit?
Five Apple Watch models can assess your blood pressure under watchOS 26. They never display it. They send an alert — a nudge that something looks off, go get it checked. Oura works the same way. Neither will hand you a systolic reading.
This isn't Apple being cautious for caution's sake. An alert stays on the wellness side of a line that a specific number crosses. "You may have signs of hypertension" is a suggestion to seek care. "Your blood pressure is 152/94" is, functionally, a diagnosis — and diagnosing disease is what makes something a medical device in the eyes of the FDA.
We know exactly where that line sits because two companies got warning letters for stepping over it. The FDA reportedly told Whoop its Blood Pressure Insights feature was neither cleared nor approved, and that it qualified as a medical device because it was intended to help diagnose or manage a condition. Whoop pushed back, insisting it was "a wellness feature, not a medical device." The FDA has sent similar letters to others, including Samsung.
So the alert-only approach isn't cowardice. It's the whole point. Apple and Oura designed around the digit deliberately, because the digit is the liability.
Vital Signals knows this line as well as anyone. Watch the footwork. The consumer Signal Ring ships now as a wellness device — no FDA clearance — while the company separately pursues 510(k) clearance for a medical-grade version designed to actually diagnose hypertension and flag dangerous trends.
Moss is candid about the sequencing. "We're launching Signal Ring as a wellness device, and we believe that's the right place to start in order to get this to consumers as quickly as possible," he told MD+DI, while pursuing 510(k) clearance in parallel.
This is the same wellness-versus-medical two-step Whoop tried. Ship the consumer version under wellness guidelines to move fast, promise the regulated version later. The difference is that Whoop's number came with an alert wrapper; Vital Signals is shipping the bare digit and calling it wellness.
The company reportedly cites a 451-person clinical study and says the ring meets ISO 81060-2, the accuracy standard for blood pressure cuffs. That sounds reassuring. But the results from the medical-grade trials haven't been published, and "tested on thousands of subjects" is a marketing sentence, not a peer-reviewed one. You are being asked to trust the number before the evidence for the number is public.
There's also a practical catch buried in the design: the math happens in the cloud. The ring can record offline, but you won't see a reading until it reconnects. A device pitched on continuous, in-the-moment awareness depends on a data connection to tell you anything.
So who is this actually for? Here Moss is more honest than his own press release. He isn't selling the ring to everyone. He reportedly aims it at older people and those a doctor has already flagged as at risk — and he tells the young and healthy to buy an Oura or an Apple Watch instead.
Sit with that. The founder is telling low-risk buyers that alert-only devices are good enough for them. Which means the Signal Ring's numerical edge only matters for exactly the people whose treatment decisions ride on that number being right — the people the FDA is most worried about handing an unverified digit.
That's the trap. The population the ring is built for is the population that can least afford a wrong reading blamed on ring fit.
The buyer verdict is not complicated. If your treatment depends on the number — if a reading might change your medication or send you to a doctor — keep the arm cuff. Keep it because it's authorized, because the AHA still endorses it, and because a cuff that's occasionally annoying beats a ring that's occasionally wrong about the one thing you bought it to get right.
Watch the trend, though. Calibration-free cuffless monitoring would be genuinely transformative if it worked and got cleared, and Vital Signals is chasing that clearance rather than pretending it doesn't need it. That's more than Whoop offered when it got its letter.
Just don't preorder the number. A ring that shows you a systolic reading feels like truth in a way an alert never will — and that feeling, not the sensor, is the product's most dangerous feature. Treat the digit as a guess with good production values until the trials say otherwise.
The founder built this to prevent the next 250. Fair enough. But the way you honor a 250 isn't by trusting a finger over a cuff. It's by knowing the difference between a number and a fact.