Emergency Communications
Japan people and others who live in places prone to natural disasters or blackouts:
Bluetooth mesh communication apps could be vital if the internet and cellular networks go down after an earthquake or typhoon.Mesh communications apps connect phones to phones, so if there's a message you want to send to somebody who's on the other side of town, that message will hop from one phone to another until it reaches its destination. It may take a while for your message to arrive, but if enough phones use the mesh app, it will eventually get there.
There are several mesh communications apps, but the one I've settled on is BitChat because it's available for Android and iOS and was developed by Jack Dorsey, who created Twitter, so he knows about communications.
BitChat messages are end-to-end encrypted.
BitChat and other mesh communications apps can work when cellular and the internet fail.