We hacked an smart-watch to run the UI based on Android Scripting Layer (android.py). This gave us the opportunity to test how slim the UI can be made and how comfortable (or not) would be to have the PassKey around your wrists.
Unlucky the first Smart-watch died unexpectedly and it was impossible to revive, so we bought another to keep testing.
We recorded a simple video to pitch the idea before another smart-watch failure. Now we're ready to go building own own hardware.