H9 Heart Rate Sensor
Polar H9 Heart Rate Sensor is a chest strap from 2020, sitting in the budget band at an indicative $59.
It reads 4 of the 33 signals this comparison tracks. Nothing at all from sleep, fitness and body composition.
By sensor class: 3 at high accuracy and 1 at consumer grade. That grade is my classification of the hardware, not a lab test. Those readings come from ECG electrodes and an accelerometer.
Rated WR30 / 30m, fine for swimming. It weighs 21 g. No subscription is required.
Budget ECG chest strap; HR + R-R/HRV over BLE/ANT+, no onboard memory.
Key specs
What it tracks
Heart & vitals
Activity
Buying for battery life? See every device ranked by battery life
Your wearable's data, read against your own normal
MyBodyAI reads COROS, Garmin, Oura, Polar and Withings by logging in, and Fitbit and Pixel Watch through Google Health. Older Garmin history comes from a data export. It learns how you usually sleep and what your resting heart rate usually is, and every day shows where you stand against yourself: recovery, sleep, load and immune scores, a biological age estimate and early warnings. Optional, and separate from this comparison.
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