[MichaelGG]

They should implement some shared key encryption for you. But I'm not sure if any systems provide building blocks. For instance, does FB login have any API for encrypting data?

The secrets they store should be offline and require manual intervention to retrieve.

Also, what's to stop a false triggering? It should require confirmation from m of n sources you specify. If I had some serious life secrets, I'd want to be very sure they don't get sent out just because I'm in a coma for a month.