The heart rate monitors in Google and Fitbit devices are insanely inaccurate during exercise. I had suspected as much already. Whenever a brisk walk indicated my pulse was 150 or so. But first, I could not reproduce this wearing a halter device and later I could not reproduce this wearing a polar heart rate monitor or a Frontier X2 ECG.

Conclusion, Fitbit and Google heart rate monitors on those wearables are hot garbage. Cue some snooty googler insisting I'm doing it wrong somehow.