A Fever-Detecting Apple Watch Pushes the Limits of Wrist-Sensor Tech

Just how many sensors can you cram into a tiny watch?

  • The next Apple Watch may detect body temperature.
  • It probably won’t be as accurate as more invasive options. 
  • The Apple Watch may be at the limit of what is possible to measure from the wrist.
person wearing apple watch and checking activity rings

Solen Feyissa / Unsplash

The Apple Watch Series 8 may be capable of detecting body temperature, but it may also be reaching the limits of what can be packed into a wrist-mounted sensor. 

After a confusing start, the Apple Watch has found its role as a fitness and health tracker and/or notification device, and Apple has gone all-in on adding sensors and algorithmic trackers. The latest report from Bloomberg's serial Apple rumormonger Mark Gurman says the next Apple Watch will pack a temperature sensor, but it also won't be accurate enough for most medical purposes.

"Apple's Series 8 smartwatch may be able to detect fevers thanks to its temperature-sensing capability, which might also bring new reproductive planning features to the device, from medical use to tracking temperature while working out or running," Vincent Amodio, CEO at Icon Medical Centers, told Lifewire via email. "However, it does not imply that you should anticipate receiving a precise temperature reading, as you would with a conventional thermometer."

Wrist-Mounted Sensors

The Apple Watch is already bristling with sensors. It periodically measures your heart rate throughout the day and can also run an electrocardiogram just by placing a thumb on the watch crown. It uses built-in accelerometers to track steps walked, but also to detect falls, track sleep, and more, and the watch can even monitor environmental noise levels. 

I don’t think smartwatches will be accurate enough to use for medical purposes.

The benefits of all this monitoring are clear. Because the watch is always there on your wrist, it can provide the kind of long-term data not possible to gather in a 15-minute visit to the doctor's office. And it can also warn you of problems and even take action. If you fall off your mountain bike in the middle of nowhere and injure yourself, the Apple Watch can (and does) call emergency services for you, for example. 

The new temperature sensor will be able to detect temperature spikes, telling you that you may have a fever, but it will not, says Gurman, be as accurate as other kinds of medical thermometers.

Temperature and Pressure

When it comes to monitoring body processes, Apple's biggest limitation is that the watch never moves from your wrist. For taking your pulse or verifying that you're still wearing your watch so it can be used to unlock your Mac or your iPhone, this placement and always-worn-ness are ideal. Ditto for determining your gait using algorithms.

But for other sensors, the wrist isn't a good spot. After all, the nurse doesn't press their thermometer to your wrist when taking your temperature.

"In general, rectal and oral temperatures are considered the most accurate," Sean Byers, healthcare specialist for seniors and resident in the Internal Medicine Program at UTMB, told Lifewire via email. "Wrist temperatures can also provide stable and sensitive measurements and a high true-positive rate, at least as compared to temperatures recorded on the forehead. I don't think smartwatches will be accurate enough to use for medical purposes, [however], they might indicate if the person has a fever, but [you] can't rely upon it."

three old wall mounted thermometers

Ilse Orsel / Unsplash

And in fact, Apple has had trouble adding more sensors to its devices. The next AirPod Pros were also rumored to include temperature and heart-rate sensors, but that plan is on hold. Apple has, over the years, tried to add other sensors for blood pressure and perhaps even blood sugar levels but has come up against the limitations of the hardware and its position on the body. 

Apple's innovation comes from a combination of hardware and software working together. The cameras in the iPhone, for example, rely extensively on custom chips inside the phones to perform algorithmic miracles on its tiny camera sensors. This is something Apple is very good at, but there's only so much you can do. Even the best algorithms need good raw data, and for that you need sensors. 

Technically, the Apple Watch is already a marvel. It can do so much and manages to do it all day long on a tiny battery. Apple will surely manage to squeeze yet more out of this little device, but it seems unlikely that there will be many major new features. And that's just fine, because the Apple Watch is already perfect for most people.

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