Like @Heretic I also tracked HRV for a while and stopped.
I even bought a device that would make it (purportedly) easy but that never worked reliably.
Then I used the iPhone as it’s been checked as ok for use with HRV4 app and eventually I stopped that. I kinda got bored checking it and wasn’t entirely sure it was telling me anything other than I’m about to die (low HRV compared to population comparisons all the time).
I am always keen on these kinds of things which means I buy stuff I end up not using/trusting.
I do kind of get the sense that after a few years of trying ‘amateur’ kit rather than proper lab testing, as an average person in an average house living an average life, unless I win millions on a lottery and then can access a serious coach/lab environment, that these half way solutions aren’t that great.
And then … the next time another thing comes along I’ll probably try that too … ahahahahahaha