One idea might be to have some way to register a 'code word' with the police/911 dispatch for a given address/phone in advance. If the code word is spoken, tha

One idea might be to have some way to register a 'code word' with the police/911 dispatch for a given address/phone in advance. If the code word is spoken, that gives extra signal that it's a genuine threat. In practice, not sure if the IT of most departments is sophisticated enough, but in theory that might help.