Luckily I don’t need anything like a bumper belt. I have trained myself to never end up on my back; to always turn a full 180° from one side to another no matter how deeply I am sleeping.

I’m able to do a number of nifty things like this in my sleep. Such as being able to wake up within 2-3 minutes of a set time, without an alarm or even a clock, so long as I get more than 4-5hrs of sleep. I’ve even been able to do it with less sleep, only with less than perfect reliability.

It’s a form of mental feedback that I do before falling asleep, and across enough days it ends up being trained in such that I don’t have to reinforce it every night.