I notice there are a number of folks wishing for o2 sensing during sleep time. There is a watch physically identical to the wyze watch called the Letsfit…and in fact is mixed in with the wyze watch when you do a search on Amazon.
It does provide all night O2 sensing and it provides a report, along with the a sleep cycle report. It has its own app, does not link with Alexa and the app is so far bulletproof for me… Same price as Wyze as well.
Try it. It’s returnable if it doesn’t suit your needs.