The Polar OH1 sensor is very comforable to wear. All the same, an Australian paper said, it is so accurate that it can be used instead of an ECG device:
There is a Polar Sensor Logger app with MQTT which should allow to connect it to Home Assistant. I tried it once, but I failed. Maybe someone more skilled and more patient than me manages to connect to sensor.
I went through the Integrations of Home Assistant ant came accross the USB Thermometer Temper, which is great. I reviewed some aspects of it on my personal website:
https://petergamma.org/usb-thermometer-temper1f/
There are Youtube videos for the TEMPer1F how to collect sensor data on an Android phone and on a Linux machine.
Does this sensor have an SDK? If so, it is really great. There is a big advantage of a sensor which can be easily connected to a Android Phone or a Linux PC, compared to other sensors, which do not allow this, for instance the Firstbeat Body Guard sensor:
https://petergamma.org/firstbeat-body-guard-and-home-assistant/
In contrast to the Firstbeat sensor, the Polar sensors have an SDK. An integration into Home Assisant would be highly desirable.
I know from my own little experience, how helpful it can be to have your heart rate on you PC or TC screen, especially if you are in trouble of letting go. Just watch your heart rate and wait until it trops.