It’s not a good day for me today, so I’ll let others fill in the details, but here’s some quick information.
.1. Official watch integrations The only official watch integration is with the Apple watch, and the only thing it does is let you turn a SmartThings routine into a widget. That’s it. Just the routines are available.
https://support.smartthings.com/hc/en-us/articles/206145893-Is-there-a-SmartThings-widget-
.2. Official Samsung Watch Integrations
There used to be an official integration with the Samsung gear two, but they never kept up with it, didn’t update it for new watch models, and I’m not sure if it still works.
.3. Garmin created by Garmin
Garmin created their own integration for their smart watch, but again, the only thing it does is let you turn a routine into a widget.
https://apps.garmin.com/en-GB/apps/b64d6aa1-121c-4e16-89d1-c49d0d42b196
.4. Third party apps
There used to be some independent third-party apps for various other watches, but I don’t think most of them still work since SmartThings changed the way third-party authorizations are done about a year ago.
There is an option for the gear S2/s3 using Tasker plus SharpTools ( so two third-party apps used in combination), but the setup is pretty complicated.
So that’s the bad news.
.5. IFTTT to the rescue!
The good news is that SmartThings does have an official IFTTT service/channel, so any watch which can run the IFTTT DO Button can turn on a virtual switch in SmartThings which you could then have trigger pretty much anything that SmartThings can do.
.6. AndroidWear 2.0 and Google Assistant
@David_Van points out below that any watch that supports androidwear 2.0 can work with Google assistant to control SmartThings devices. I just don’t know how well it works with U.K. Accents.
.7. A community-created Gear 3 app is in development, but not yet released
And there is a community member working on a Samsung gear three app. He is running a private beta right now. You can find discussion of this in the following thread:
The IFTTT app and the official widget options should definitely work in the UK. I don’t know about the other options mentioned above.
My personal experience with Apple Watch
Personally, I have an Apple Watch and use it all the time, but not so much with SmartThings, although I do use the IFTTT Do Button occasionally.
Again, just speaking for myself, I really like the Apple Watch. I use it for voice texts, HomeKit, Reminders, notifications, shopping list, health tracking, Apple Pay, even the occasional phone call. It Is physically much easier for me than the phone. But everyone is different.
Personally, as far as SmartThings goes, I think having two or perhaps three frequently used routines as widgets is convenient, but I don’t know that it would be enough to justify a watch in and of itself.
Summary
If you’re getting a smart watch for other reasons, you will probably be able to use widgets to run SmartThings routines, although the method may vary depending on the specific watch model. If the watch can run the IFTTT app, you can associate an IFTTT “button” with anything that SmartThings can do via IFTTT.
If Google assistant works well for you, that can give you voice control of smart things control devices on any watch that supports androidwear 2.0
But at the present time I wouldn’t buy a smart watch just for use with SmartThings – – functionality is pretty limited.
(If your devices are also HomeKit compatible, then an Apple Watch Is very useful. But there aren’t many UK devices that work with both HomeKit and SmartThings other than the Phillips hue bridge.)
Follow ups will have to be handled by other people, but I hope that’s enough to start with. 