It looks like there isn't a good fitness tracker to measure HRV. They aren't precise enough. It would be necessary to use a chest strap. I don't believe I'll be

It looks like there isn't a good fitness tracker to measure HRV. They aren't precise enough. It would be necessary to use a chest strap. I don't believe I'll be able to do it with my cheap Mi Band 2. Does anybody here know about a good fitness tracker to measure HRV?