> The solution is actually pretty easy: require a pairing procedure that can't be done remotely. For example, the Nest app on a phone could display a QR code with is public key fingerprint, which you show to a camera, and the camera will only send video to phones it's been paired with. That would pretty much completely eliminate this failure mode.

This is how Tesla pairs a new phone to work as a key -- you need to have one of the two RFID key cards that come with the car present, and be inside the car with the new phone. You pair _that particular device_ and then authorize it with the RFID card. Simply having the login to the app/account is not enough, and from the car itself you can always remove a paired phone.

A key for a car frames the problem in much clearer terms and Tesla engineered a secure solution. It is unfortunate this isn't done for other things where security is equally important.