I see in the docs, that an app can figure out, if sleep mode is on or off. But not any new custom focus modes (available on newer devices).
I had the idea to track study time with an app, after creating focus modes, with different watch faces (e.g. reading, listening to target language I'm learning). I can set different watch faces for focus modes, so if an app could figure out which watch face is on currently, that could work too.
Or, if I could make my own watch faces for this, which somehow signal to the app when, how long they were displayed.
I just don't see a way to do this now, I might be missing something.
I can just create an app with a simple timer for this, or create activities (what if I do listening activity while hiking? Two activities can't run in paralell), but using focus modes would be really nice.