If said service requires passwords to all of my accounts, then, no, for reasons others have mentioned. But what about a slightly different model: Panic Button

If said service requires passwords to all of my accounts, then, no, for reasons others have mentioned. But what about a slightly different model: Panic Button service makes deals with Facebook, Google, & other big players[1] which create channels for Panic Button to be able contact them and change passwords or lock accounts on behalf of a user, but Panic Button doesn't actually store passwords for these services? When a user wants a lockout, they contact the Panic Button service, via at least 2-factor authentication, possibly more. [1] No doubt rather difficult.