I was having a conversation with some friends the other day about what schemes might mitigate some of these risks, something like an anti-safe word, i.e. a "danger word" that someone can be used to remotely validate that a loved one is authentically in danger.

This is fairly low-tech and likely susceptible to various kinds of social engineering, but I'm curious what a more robust approach might look like that doesn't involve us all regurgitating 6-digit codes like robots all the time.