I’m still pretty new with OpenHab but I do have a Tasker task set to send an MQTT message when it recieves a certain intent from another app. OpenHab (running on my pi) currently doesn’t do anything with it, though. Haha
Not from a watch, but I send tasks to openHAB from Tasker using openHAB’s REST API. If you search the forum for “Tasker” you should find a few examples.