Hi everyone, I built khazan for a very specific person: a worker who walks into a steel tank, a basement or a tunnel, and loses every bar of signal the moment he goes in. If something goes wrong down there, he has no way to call anyone, and the people on the surface have no way to know. khazan turns the phones themselves into the network. Messages travel over Bluetooth from phone to phone, so a message can cross a site by passing through coworkers standing in between. If one of those phones does have internet, the message can continue out to a supervisor who is far away. And SOS does the loud, simple thing: an alarm on every phone in range. Three decisions I made early and kept: - No account. No phone number, no email, nothing to sign up for. Your identity is a key on your device. - End-to-end encryption. Messages are not stored on a server, because there isn't one. - It has to work when everything else has failed. That is the whole point. Being honest about the limits, because they matter more than features here: - Bluetooth range is Bluetooth range. Without someone in between, a message waits. - The Bluetooth advert carries a username, so presence is not anonymous even though content is encrypted. - Android only today. - It is not a certified emergency system. It alerts your coworkers, not emergency services. It's free, no ads, no subscription. I'd genuinely like to hear from anyone who works somewhere with dead signal: what would you need before you'd trust this on a real site?

khazan

Bluetooth chat and SOS for places with no signal

Bluetooth chat and SOS for places with no signal