A while ago I had a polar h10 to use with sleep as android, and after trying it for a few nights, it would get so uncomfortable that it wakes me up usually 4 or 5 hours later because of my sweat making the electrode part all sticky and created friction against the skin on my chest when breathing, and would be too uncomfortable to fall back asleep with that I just take it off and return to sleep(I could wipe the sweat away but that means always having interrupted sleep), and I did try making the strap looser but that made it easily slip down and not have good enough contact with skin to make accurate heartrate measurement. another thing I tried was to sleep with it over my shirt and just use the motion sensor but I found out the motion sensor won’t function unless the strap is making contact with your skin, this is what finally lead to me returning the polar h10 for a refund. right now I suggest to use polar Oh1 for more comfort since it just goes on your arm, But I recommend to wait for the polar verity sense to get tested if you want better battery life.
Why I don't recommend the Polar H10 for sleep tracking comfort wise
Thanks for info.