Even if that's added in watchOS 7 (which is what I'm guessing you meant, not iOS 14 alone), what would be required is a software mechanism to alert the user below a particular threshold. Given Apple's history, I doubt if this feature would be enabled for currently sold devices even if the hardware supports it. Apple may have its own reasons not to support certain features available in hardware, including reliability factors, and not just profit motives alone. So I'm kinda doubtful of the feature being enabled and working as the GP described in the devices being sold now (before new versions arrive later this year).
Sorry to be specific what I meant was that iOS14 has an API to read pulseox readings from an Apple Watch and then you can do what you want with it (like make an app to alert on it).
Presumably yes it would need support in WatchOS 7.
Thanks. In a previous comment you said that “The oxymeter beeped and woke me up.” Is this the same oxymeter? I read the FAQ for the FL350 and it doesn’t have an alarm.
I double checked and the one I use is an old model (FL100) that appears to have been discontinued. The FL350 mostly resembles it, though it appears you are correct that the FL350 does not have an alarm. My apologies for the misdirection.