Our first idea is a hardware pendant in a shielded case

It is a computer containing radio, wifi and data in an emergency

It works with multiple communication protocols and can work offline with p2p interactions

... ...

It will have a knowledge bank of essential human knowledge and can be used as a computer

Build one yourself or buy one.

This is an open idea so feel free to contribute and help. It isnt nice but if we establish fallback systems we can still communicate if an unexpected event occurs.