This is the problem with the modern "app" way of doing things. This sort of thing would be best handled as a website so that users need not run specific software on thier phones. Reports can come in as basic emails parsed for a lat/long or grid. Then a kml file can be pushed as needed to a basic web-facing map. The bandwidth would be minimal and very resistant to shutdown. Heck, share the kml files via torrents or put the map server in tor if necessary. No apps required.