There is active work by SmartThings community members on in the Samsung SmartThings forum to release a Gear S2 /S3 app to control Samsung SmartThings (Routines, and also devices - aka "Things").
The first release is getting close, the main developer is finalizing some changes and then will likely release a v1 and open source (GitHub) so that additional work can be completed by other SmartThings owners who would like to contribute.
Thread on Gear app development in SmartThings forum is here:
https://community.smartthings.com/t/gear-watch-smartthings-app-development-thread/73122
The first release is getting close, the main developer is finalizing some changes and then will likely release a v1 and open source (GitHub) so that additional work can be completed by other SmartThings owners who would like to contribute.
Thread on Gear app development in SmartThings forum is here:
https://community.smartthings.com/t/gear-watch-smartthings-app-development-thread/73122