Sleep tracker - how to google the most accurate ones?

Question

Health and computer

I used Xaomi Mi Band 1 and 2.
They consider the beginning of sleep to be the moment when they lay 10-15 minutes in bed.
Whether you fell asleep or not.
How can you google more accurate sleep trackers?

Answer 1

https://www.barbellmedicine.com/placebo-sleep/
The findings showed that subjects who were told they had slept poorly tended to perform worse on the cognitive testing, compared to subjects who were told they had slept better — regardless of how they actually thought they slept! In fact, the “assigned” sleep condition is better predicted how subjects performed than the subjects' own assessment of how they slept.
Does not work
You always sleep and get enough sleep perfectly with a plus