Severe weather alerts
Setting this up takes about a minute. The slow part is not the software — it is deciding what to call yourself, because the handle ends up on a poster and cannot be changed afterwards.
Three rungs, and each one costs something
Normal is a notification in the shade and needs no permission at all. Important is a heads-up banner with a sound, if the subscriber allowed this channel that. Urgent may take over the screen, override Do Not Disturb and be read aloud — each granted separately, each refusable. The rung is a ceiling rather than an outcome, and it is also a budget: a channel that spends Urgent on a car-park closure loses the permission the same afternoon, from the only people who could have granted it.
Draw a circle without knowing who is inside it
You place a centre and a radius on a map, and the circle travels attached to the alert. Every subscriber’s phone receives it and compares its own position locally, then decides whether to show it. No subscriber position is ever sent to us, which is why this is a design fact rather than a promise: there is no column anywhere that could hold one. Two consequences follow deliberately. A geofence only ever narrows — it cannot add somebody who did not subscribe. And it fails open: a phone that cannot work out where it is shows the alert rather than hiding it, because missing an evacuation is worse than seeing one meant for the next street.
Draft, schedule, send — and what cancelling cannot undo
Composing and sending are deliberately different permissions, so the person or script that writes an alert can be forbidden from publishing it. A scheduled alert becomes visible at its time without anything having to run at that minute, which means a server that was briefly down delivers late rather than never. Cancelling is honest about its limits: it stops an alert reaching phones that have not fetched it yet and does nothing at all to the phones that already have it. An alert cannot be unsent.
Questions, answered plainly
When should I use urgent priority?
When somebody needs to act in the next few minutes: an evacuation, a lockdown, a genuine safety instruction. Not for a schedule change, and not for anything that would still be fine to read an hour later. Urgent is granted by subscribers one at a time and withdrawn just as easily, so it behaves like a budget rather than a setting.
Do you know where my subscribers are?
No. The circle is sent with the alert and each phone compares its own position locally. We hold no subscriber location, so there is nothing to leak, subpoena or lose. A phone that cannot determine its position shows the alert rather than hiding it.
Can I unsend an alert?
No. Cancelling stops it reaching phones that have not fetched it yet, and does nothing to the ones that already have it. Compose as a draft and read it back before you send; that habit is worth more than any undo button we could offer.
Do subscribers need an account?
No. They install the app, subscribe to a handle, and that is the whole of it. Only the person running the channel signs up for anything.
Say it once. Every subscribed phone gets it.
Free up to 100 subscribers, no card to start, and the handle is yours permanently.
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