No idea how it compares, but my local Lidl was selling a smart ring for $15 so I decided to give it a shot. I assume half the measurements are "for entertainment purposes only" (glucose, blood pressure, stress [heart rate variability proxy?], blood oxygenation [might be ok with my skin tone, not sure I'd trust it]) but the others seem fairly accurate. Again, no idea how it compares to the pricier ones, but seems to match my pulse measured at neck and what I remember of my nightly sleep pretty well.

And yeah, I'm certainly not going to worry about it getting scratched or slightly wet. Actually, it got dropped and stepped on, and is slightly dented but still seems to run fine - the epoxy sealant for the electronics seems intact and while I was a bit concerned for the battery, that's been a while with no issues.

And, while I have no idea whether the app is quietly collecting data and pushing it to a server in china (if it is, it is doing it in a way that is sneaking past the firewall), at least it does not require creating an account to use.

So in that sense it is maybe more private than oura or samsung ?