How it works
Why a screenless wristband lasts 45 days on one charge
Why a smartwatch needs charging daily but a screenless band lasts 45 days: what drains it, how Bluetooth saves power and why the phone does the maths.
sleep
How your band guesses whether you're in deep sleep or REM
Without seeing your brain, a band slices the night into 30-second chunks and guesses your sleep stage from pulse, HRV and movement. Here's how it works.
sensors
Pulse with light: how a wristband reads your heart from outside
How a wristband knows your pulse using only light: what photoplethysmography (PPG) is, how it works out pulse, HRV and SpO2, and why it sometimes errs.