I can see two options, hooking into the existing buttons, or broadcast events.
You’d have the option for a dedicated button like current, or have a button launch the HD Radio and trigger an output.
Or I can broadcast events, such as HD Radio being enabled/disabled, and have a way to monitor and act upon it. I think that would be more flexible. I need to think of a UI for it. That’s the hardest part for me.
I like the second idea, more. I could send events for just about everything, and you can act upon those events with hardware one way or another.