The most useful apps, tools and sites we used during Hurricane Irma, as compiled by a journalist in Tuscaloosa, Alabama experiencing Hurricane Irma blowing over. Try This! — Tools for Journalism. It's interesting that he liked Facebook Messenger so much - I so prefer WhatsApp for text messaging.
Another list: 5 best apps for helping during a hurricane.
But here's what I'm more interested in: apps that help people AFTER the hurricane, after the disaster. It's in the days after the hurricane that people become truly desperate. But I'm not sure "there's an app for that." GasBuddy would be helpful, but what else?