Please don't tell me to move while I'm sleeping :)

Sleep is detected through the lack of movement of the accelerometer. The 735 can't tell the difference between you sleeping and you sitting still on the sofa needing to get off your butt! You need to change the sleep time if you want to stop the move alert.

HTH

CW

The watch knows I was sleeping,

As far as I understand how it works, no, it doesn't.

because it accurately tracked it,

I'm afraid your conclusion is logically erroneous.

It is the cloud-based Garmin Connect service's responsibility to determine if you were sleeping, after the fact, using movement data captured and uploaded by the watch. That does not happen in real-time, especially in the absence of a continually active Bluetooth connection between the FR735XT and the mobile device running the Garmin Connect Mobile app; and, even after Garmin Connect has received and analysed a batch of data uploaded by the watch, the service (or app) does not then attempt to send information back to the device to tell it whether you're sleeping or not.

Turn on do not disturb whilst on vacation!

As far as I understand how it works, no, it doesn't.

I'm afraid your conclusion is logically erroneous.

It is the cloud-based Garmin Connect service's responsibility to determine if you were sleeping, after the fact, using movement data captured and uploaded by the watch. That does not happen in real-time,

Hohum, perhaps you're right, in which case this top-end watch is more gutless than the $99 pebble I had before, which actually could do sleep detection on the watch. :/

And all this makes me realize maybe I may have purchased yet another IoT device which will lose many of its features the moment the cloud overlords choose to eliminate some services. :(

If you bought a 735 to be a top of the range sleep tracker you will undoubtedly be a little disappointed as that is not its primary purpose - this being of course a high-end device for triathletes and/or runners.

Anyway sounds like this particular problem won't be one next week...

If you bought a 735 to be a top of the range sleep tracker you will undoubtedly be a little disappointed as that is not its primary purpose - this being of course a high-end device for triathletes and/or runners.

Well, I had a high-end device for triathletes and/or runners (and swimmers); a Fenix 2...

I recently bought the 735XT for the additional things the Fenix 2 didn't have, including activity tracking - which includes steps, sleep, etc as advertised, right?

Anyway sounds like this particular problem won't be one next week...

Why is that? Because I'll be off vacation? ;) Well, I guess that's one solution.

The FR735XT is not designed or marketed to be a “top of the range sleep tracker” or “high-end 24×7 activity tracker”. It has activity tracking features, but that does not mean the device does it particularly well. Then, it does monitor your sleep as advertised – by physically acquiring and recording information while you sleep – but does not perform any analysis or reporting on its own, or use the information to make decisions and/or vary its own behaviour; monitoring does not imply both components of sense-and-respond.

The FR735XT is not designed or marketed to be a “top of the range sleep tracker” or “high-end 24×7 activity tracker”. It has activity tracking features, but that does not mean the device does it particularly well.

The watch is marketed as containing an "Activity Tracker" which performs "Sleep Monitoring (monitors total sleep and periods of movement or restful sleep."

You say that actually performing these tasks would require a "top of the range" or "high-end" device, but it is exactly what the watch claims to do, and I would argue that "monitoring sleep" is actually a very low bar for a device claims to perform "Sleep Monitoring," no?

Look, the watch does some nice things, for sure. Depending on cloud computing to detect contiguous nighttime inactivity as "sleep" is not one of them, IMHO.

it does monitor your sleep as advertised – by physically acquiring and recording information while you sleep

If we're going to play semantic games, fine, but then it should advertise itself simply as a "motion recorder" not a "sleep monitor" right?

Well, whatever. It's too bad they didn't put a little more effort and thought into the tracker side of the watch, to make this side of the functionality more robust even if it's not the sole or primary functionality. I'd hoped for a little more sophistication out of a $450 device, TBH.

Well looking at my last few day's sleep on GC then there does seem to be some "sophistication". It shows fairly accurately my actual going to sleep and getting up times and I even got recorded sleep after my "normal" getting up time. There is also indication of deep sleep, light sleep and awake.