It would be so convenient to use Sesame from my Apple Watch. It seems like a natural fit.
The UI should be very simple. One button to toggle the lock / unlock state. Force touch to change locks. No other features are necessary – everything else should be done from the phone side. The actual Bluetooth communication side of things can happen from the full app on the phone.
Main screen:
IMG_0096.png
Force touch:
IMG_0095.png