From Anonymous on 2015/02/19 13:22:08 +0000
I like to have my Phone on airplane Mode over night. Reenabling Bluetooth for sleep tracking works, but defeats the purpose. I think a “stand alone” app for the smartwatch would be great. Alarm by smart watch vibration, sleep tracking on watch and the next time the watch is connected with phone the record is uploaded… kind of the same way the Sony SW3 can be used as standalone for running and HR recording with ghostracer app.
Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/7114362-smartwatch-records-offline
From Dave on 2017/01/20 10:28:22 +0000
Please use the Android Wear menu "Help & feedback" to ask Google for this!
Sleep as Android support wrote that they need Google to create this.
Here's why:
"Theoretically it would be possible.For us it would be ~1 year of developement. It would only work on half of the market (only on watches with sensor batching) and if not implemented by Google directly battery consumption would be very high"
So let's all write to Google using the Android Wear menu "Help & feedback" to tell them we want this 
From Dave on 2017/01/19 16:38:27 +0000
It's exactly how Pebble does (works great!) - and the Android smartwatch Polar M600 too.
From Maxence Leduc on 2015/08/03 09:39:06 +0000
Pleeeaaase, add this feature ! Having an offline mode would also prevent the phone from being awaken all night, so we could even use SleepAsAndroid without the phone to be charging !
Agreed! - since Pebble shut down its servers there’s been no smartwatches with flight-mode sleep detection.