Not sure how you could work in a background service. If your temporal event runs at the top of the hour, requestApplicationWake() might be ignored as the watch face is already running. The user may be asked about the request, but then you have the question and not the WF. The background could do an exit() that would then be seen in onBackgroundData(), and there the main app could do a WatchUi.requestUpdate() but the WF is already getting regular onUpdate() calls.
Add to that the background service will stop the WF saving it's properties, so can't really be used which is why I was looking for another way.
What would be great was if there was a way for the WF to simply run without display, ie not actually sleep but just be dormant [paused] pending a timer event, which can then record punctual information in the settings/properties.
Never heard of an issues where the background prevents saving properties in the watch face itself. I have a few apps that do that There may be an issue on some devices saving them from the background itself.
Sounds like you may want a device app instead of a watch face
