FireChat

FireChat was a proprietary mobile app, developed by Open Garden, which uses wireless mesh networking to enable smartphones to connect via Bluetooth, Wi-Fi, or Apple's Multipeer Connectivity Framework without an internet connection by connecting peer-to-peer.
Though it was not designed with the purpose in mind, FireChat has been used as a communication tool in some civil protests.
FireChat is now discontinued. The official URL is a 404 error page, and apps have not been updated since 2018.
History.
The app was first introduced in March 2014 for iPhones, followed on April 3 by a version for Android devices.
In July 2015, FireChat introduced private messaging. Until then, it had only been possible to post messages to public chatrooms.
In May 2016, FireChat introduced FireChat Alerts to allow users to send push alerts during a specific time and place. This feature was aimed for aid workers doing disaster relief and was developed from a partnership with Marikina a city in the Philippines.
Usage.
FireChat first became popular in 2014 in Iraq following government restrictions on internet use, and thereafter during the 2014 Hong Kong protests. In 2015, FireChat was also promoted by protesters during the 2015 Ecuadorian protests. On September 11, 2015, during the pro-independence demonstration called Free Way to the Catalan Republic, FireChat was used 131,000 times.
In January 2016, students protested at the University of Hyderabad, India, following the suicide of a PhD student named Rohith Vemula. Some students were reported to have used Firechat after the university shut down its Wi-Fi.
The current version (Oct 2018) seems to be a fork of riot.im.
Security.
In June 2014, Firechat's developers told "Wired" that "[p]eople need to understand that this is not a tool to communicate anything that would put them in a harmful situation if it were to be discovered by somebody who's hostile ... It was not meant for secure or private communications."
As of July 2015, FireChat claims to use end-to-end encryption to protect its one-to-one private messages.