Rest tracking in watchOS 9 gives even more insights Using the introduction of slumber stages. Apple Watch uses signals from the accelerometer to estimate when consumers are in REM, Core, or Deep slumber. Looking for a smooth steel up grade from The essential silicone band your Apple Watch came with? https://why-strap-for-apple-watch64218.csublogs.com/32720779/5-tips-about-invicta-watch-band-remove-link-you-can-use-today