Heart rate variability: what your watch is measuring
HRV is the tiny variation in timing between heartbeats. Wearables use it as a signal of recovery and stress. Here is how to read the number.
Health and wellness tech
Wearables, sensors and health software, and what their numbers mean.
How continuous glucose monitors work
A CGM reads glucose from the fluid under your skin every few minutes. Knowing what it measures explains why it sometimes disagrees with a fingerstick.
How smartwatch blood oxygen readings work, and where they fall short
A watch estimates blood oxygen by shining red and infrared light into your wrist. The method is sound and the wrist is a hard place to do it.
VO2 max on your watch: how it is estimated
The lab test needs a mask and a treadmill. Your watch works it out from pace and heart rate. Here is what the estimate is good for.
What a sleep score measures, and what it guesses
Your wearable turns a night into a number out of 100. Some of the inputs are solid measurements and some are estimates.
August 2026: the first smart ring cleared to flag sleep apnea risk
Samsung's Galaxy Ring got FDA clearance for a feature that checks two nights of breathing data. It screens for risk and does not diagnose.
Oura Ring 5: a thinner ring and a step toward the clinic
The June 2026 model shrank the hardware and added a way to bring lab results into the app, at a starting price of $399.
May 2026: a $99 Fitbit with an AI coach, and Whoop adds doctors
Google and Whoop made opposite bets in the same week on who should interpret your health data: software or a clinician.
What the FDA's 2026 wellness rules let your wearable tell you
A January guidance opened the door for watches and rings to estimate blood pressure and glucose without FDA review, as long as they stay away from diagnosis.
Apple Watch hypertension alerts: what the FDA cleared in 2025
The feature does not measure blood pressure. It watches a month of heart sensor data for a pattern and tells you to get checked.
The FDA's warning to Whoop over blood pressure estimates
In July 2025 the agency said a wearable that estimates blood pressure is a medical device, whatever the disclaimer says. Whoop disagreed.
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