A non-invasive way to measure blood glucose that actually works
For years, the dream of a wristwatch that could silently read your blood sugar has lived somewhere between science fiction and medical necessity. Now, through a quiet but revealing financial disclosure, the outlines of that future are becoming visible — Apple, partnering with British sensor firm Rockley Photonics, appears to be assembling the technology that could bring non-invasive glucose monitoring to millions of wrists, potentially reshaping how humanity manages one of its most common chronic conditions.
- The stakes are high: continuous glucose monitoring currently costs diabetics over $1,200 a year in external hardware, locking a life-changing tool behind a significant financial barrier.
- SEC filings expose Rockley Photonics' near-total financial dependence on Apple, strongly suggesting the two companies are deep in a partnership that goes far beyond casual supplier arrangements.
- Rockley's optical sensors promise a leap in precision — up to a million times sharper resolution than existing wearable LEDs — but translating laboratory capability into a reliable, battery-efficient consumer device remains a formidable engineering challenge.
- Apple Watch 8, likely arriving in 2022, is now the target horizon, with Apple choosing deliberate patience over a rushed and potentially dangerous early release of health-critical technology.
Apple has been quietly pursuing blood glucose monitoring for its watch since at least 2017, when Tim Cook was spotted wearing a prototype on campus. Heart rate, blood oxygen, and ECG features have come and gone in successive models, but glucose — the metric that could most profoundly affect millions of lives — has remained just out of reach.
The path forward may run through a British company called Rockley Photonics. When The Telegraph examined Rockley's SEC filings ahead of its public offering, one detail stood out sharply: Apple is by far the company's largest customer, accounting for virtually all of its revenue in both 2019 and 2020. That level of financial dependency points to something deeper than a routine supplier relationship.
Rockley's technology is the reason for the interest. Its optical sensors can detect a remarkable range of biological signals — glucose, lactate, blood pressure, oxygen saturation, core body temperature, and more — without any needles or external medical hardware. The company claims its lasers operate at resolutions far beyond what current wearable LEDs can achieve. Rockley's CEO has said he expects the technology to appear in consumer products by 2022, though he stopped short of naming Apple as the launch partner.
The human case for this feature is compelling. Beyond the millions managing diabetes, there is a growing population of people who simply want to understand how food and lifestyle affect their metabolic health. A built-in sensor on a device already worn by tens of millions could democratize access in ways a $1,200-per-year external device never could.
Still, the obstacles are real. Sensor accuracy must be airtight — erroneous glucose readings carry genuine medical risk. Battery life, already a pressure point for Apple Watch, would face new strain. And a significant price increase on the Watch 8 could limit the very accessibility that makes the feature meaningful. Apple, characteristically, appears to be taking its time — betting that a right answer in 2022 is worth more than a premature one now.
Apple has been chasing blood sugar monitoring on its watch for years. Tim Cook was spotted on campus wearing a prototype as far back as 2017. The company's engineers have tracked heart rate, oxygen levels, and electrocardiograms, but glucose—the one metric that could genuinely change lives for millions of people—has remained out of reach. Until now, perhaps.
The breakthrough isn't coming from Apple's labs. It's coming from a British sensor company called Rockley Photonics, which is about to go public. When The Telegraph dug through the company's SEC filings, a striking detail emerged: Apple is Rockley's largest customer by a significant margin. In 2020 and 2019, Apple and one other customer accounted for essentially all of Rockley's revenue—100 percent and 99.6 percent, respectively. That's not a partnership. That's a dependency.
Rockley makes optical sensors that can read multiple biological signals without requiring medical-grade equipment. The company's technology can detect lactate, alcohol, carbon monoxide, blood pressure, oxygen saturation, core body temperature, and glucose. The lasers involved are extraordinarily precise—up to a million times higher resolution than existing LED solutions in wearables, according to the company's own claims, with accuracy a thousand times better and a hundred times broader wavelength range. For Apple, the appeal is obvious: a non-invasive way to measure blood glucose that actually works.
The timing matters. Rockley's CEO, Andrew Rickman, told The Telegraph he expects the technology to appear in consumer products next year—meaning 2022. He wouldn't confirm whether Apple would be the first to use it, which is exactly what you'd expect from someone bound by Apple's legendary secrecy agreements. But the math is straightforward. Apple Watch 7 is coming this fall. The model after that, the Watch 8, is when this sensor is likely to debut.
Why does this matter beyond the tech specs? Because the current alternative is brutally expensive and cumbersome. People with diabetes who want continuous glucose monitoring today have to buy a separate device—a transmitter and disposable sensors that cost roughly $1,245 per year. That's not accessible to everyone. A built-in sensor on a device millions already own could change the equation entirely. It would also appeal to people without diabetes who are curious about how their diet affects their blood sugar, or who want to optimize their metabolic health. Apple could market it as a wellness feature, not just a medical tool.
But there are real obstacles. The sensor technology has to be reliable—false readings could be worse than no readings at all. There's the question of battery life; adding power-hungry optical sensors to a device that already struggles to last two days is a genuine engineering problem. And then there's cost. If the Watch 8 becomes significantly more expensive because of this feature, adoption could stall. That's probably why Apple isn't rushing. The company would rather get it right in 2022 than ship something half-baked in 2021.
Citas Notables
Rockley's two largest customers collectively accounted for 100% and 99.6% of Rockley's revenue in 2020 and 2019, respectively.— Rockley Photonics SEC filing
Rockley CEO Andrew Rickman expects the technology to be in consumer products next year, though he would not confirm whether it would be in an Apple product.— Andrew Rickman, Rockley Photonics CEO
La Conversación del Hearth Otra perspectiva de la historia
Why would Apple care so much about blood sugar monitoring? It's not like everyone needs it.
True, but the people who do need it—diabetics—have been waiting for this for years. And Apple sees a bigger market: anyone interested in how food affects their body. It's the same reason they added ECG to the Watch. Start with medical necessity, expand to wellness.
So Rockley is basically betting its entire company on Apple?
Essentially, yes. Apple is their largest customer by far. That's both a blessing and a curse. It means they have a guaranteed buyer, but it also means they're completely dependent on Apple's timeline and decisions.
What's the actual technical challenge here? Why hasn't this existed before?
Measuring glucose non-invasively is genuinely hard. You need to shine light through skin and read the signal bouncing back. Most wearables use LEDs, which aren't precise enough. Rockley's lasers are orders of magnitude better. But "better" doesn't automatically mean "ready."
And if it works, what changes?
Everything, potentially. Right now, continuous glucose monitoring costs over a thousand dollars a year. If it's built into a watch most people already own, the barrier to entry disappears. Diabetics get better data. Everyone else gets insight into their metabolism. That's a real shift.
But Apple could just decide not to use it, right?
They could. Or they could decide the battery drain is too much, or the cost is too high. That's why Rickman was cagey about confirming Apple would use it. He knows Apple could walk away at any moment.