Product

How DEV.B works

People often see a flood, landslide or fire before any official system does. DEV.B lets one person raise the alarm and lets the people nearby check it, so a warning can spread quickly, even without a phone signal.

How it works

  1. Someone sees danger. They press the big red button, pick the hazard and send. A short note and a photo are optional.
  2. Phones nearby ask "Do you see it?" They show the type of danger and how far away it is. People answer with one tap: yes or no.
  3. The answers are weighed, not just counted. A "yes" from someone close by counts more than one from far away. A photo counts more. Answers that arrive all at once from the same spot count less, because they may be fake. The app also notices when many people nearby have not confirmed.
  4. The warning level rises as enough different people confirm. Each person who confirms passes the alert on to the phones around them.

We tested this method on thousands of simulated villages. Where enough people nearby have the app, almost every real danger was confirmed and false alarms were rare. Where very few people have it, most reports stay at "Possible danger", because too few people can confirm them.

Alert stages

Possible danger: someone reported something nearby. You are asked whether you can see it.

Be ready: at least two different people nearby have confirmed it. You see an amber screen with a two-tone chime. Pack water and papers, and charge your phone.

Danger confirmed: at least three different people have confirmed it and the evidence is strong. You see a red screen with a siren and vibration. Follow your local authorities.

Each level has its own colour, shape and sound, so it can be understood without reading and without seeing colour.

Hazard types

You can report five kinds of sudden, local danger: flood, landslide, fire, dam failure and building collapse. Each has a simple picture, so you don't need to read to choose.

Offline mode

DEV.B is built for the moments when phone towers and internet are down. Reports, answers and alerts travel directly between phones over Bluetooth, and the safety guides are stored on the phone. If you send a report while no one is in range, your phone keeps it and passes it on as soon as another DEV.B phone comes near.

Bluetooth relay

  • Each phone passes an alert to DEV.B phones in Bluetooth range, and they pass it on further. An alert can travel up to 7 hops from the first phone.
  • Alert messages are tiny, so they travel quickly and use little battery.
  • In a crowd, only a few phones re-send each alert, so phones don't drown each other out. Where phones are few, every phone re-sends.
  • Phones hold alerts for up to 6 hours, so someone who arrives later still gets warned.
  • Relay phones are phones left plugged in with the app open at a school, clinic, place of worship or market. They help connect spread-out villages.
DEV.B keeps passing alerts on in the background, unless you close the app by swiping it away. On Android a small permanent notification shows this. iPhones limit Bluetooth when locked, so locked iPhones find each other more slowly.

SMS fallback

Planned. When mobile data is down but text messages still work, DEV.B will be able to send alerts by SMS. This is not available in the current version.

Shelter map

The map shows reported dangers and nearby shelters, with walking distance and direction. In the current test version the shelters are examples. We plan to add real shelters from public sources and local partners. Shelter information may be incomplete, so always check with local authorities.

Safety guides

Short, simple steps for before, during and after each hazard, plus an emergency bag checklist. Saved on the phone, so they work without internet.

Languages

DEV.B is available in 30 languages. When you choose your country, the app switches to its language, and you can change the language at any time: English, Español, Français, Português, Русский, العربية, فارسی, پښتو, اردو, हिन्दी, বাংলা, नेपाली, རྫོང་ཁ, བོད་སྐད, සිංහල, தமிழ், မြန်မာ, ไทย, ລາວ, ខ្មែរ, Tiếng Việt, Bahasa Indonesia, Filipino, 中文, 日本語, 한국어, Kiswahili, አማርኛ, Kreyòl ayisyen and Türkçe.

Most translations are first drafts that native speakers are now checking. If you speak one of these languages, you can help. Need another language? Ask us.

Accessibility

The main actions need no reading: one big red button to report, and large green and grey buttons to answer. Alert levels differ by colour, shape and sound. See our accessibility statement.

Release notes

Test version · October 2026

  • Reporting, "Do you see it?" confirmations and three alert levels.
  • Phone-to-phone Bluetooth relay with store-and-forward.
  • Choose your country and language (30 languages).
  • Emergency numbers you save yourself, with a confirmation before calling.
  • Optional photo for rescuers, stored only on your phone.
  • Offline safety guides and an emergency bag checklist.

DEV.B is not yet published in the App Store or Google Play.