In the wake of the recent wildfires in southern California, Watch Duty—a simple, free app that provides real-time fire maps and alerts, and which prizes, and is prized for, accurate data, collated by its volunteer reporters—has become the most popular app on the App Store and is being hailed as an essential lifeline: see The Hollywood Reporter, The New York Times, Rolling Stone, The Verge, Washington Post (paywalls on some links).