Hey thanks for your reply! Yeah, I do need live updates. I need to be able to detect REM sleep through an algorithm I developed that requires movement, heart rate and oxigen saturation. So yes, I could wait for the watch to signal the user is asleep to begin monitoring, but then I will need relatively continuous monitoring.
One thing I was thinking to try was: When asleep do a check, if certain conditions are met, continue monitoring, otherwise do another check in 5 minutes. If conditions are met, do continuous monitoring for a while, in order to determine if you are in REM or not.
Thanks for the link, I will look into it. If my explanation bring out other ideas, I'll look into them as well!