I bought a camera the other day with the nifty feature of having an NFC tag embedded in it to guide your phone to launching (and installing, if necessary) the companion mobile app.

It occurred to me that this is a really good way of establishing a trust path: while they're only using it to guide you to the right app, they could embed a little public key in there. Then you could authenticate the new printer or fridge by physically being near it.

We'd have to extend our UIs a bit to cover these use cases (it should basically act like a trusted self-signed cert), and probably you only want to trust NFC certs for *.local.