Thanks, Carbonfiberboy.
I'm in a bit of a quandry here over just which direction to take. I like the idea of the Polar H10, but it seems like the way to assess Afib in particular is the Kardia EKG sensor. The manufacturer says (in the Amazon Q&A) that it's not certified for HRV. There doesn't seem to be a way to get data out of it into the Elite App.
The EliteHRV app folks have a list of preferred HR sensors, and they don't mention the Kardia or any of the other devices that do an at-home EKG and can label other irregularities. It looks like either the Polar H10 or H7 - which I think is just an older model.