Meshtastic® is a project that enables you to use inexpensive LoRa radios as a long range off-grid communication platform in areas without existing or reliable communications infrastructure. This project is 100% community driven and open source! Each Meshtastic node acts as a repeater and will rebroadcast every message to other nodes in the network that it can reach. This is a great way to communicate with others in your area when all other forms of communications are down. It does NOT require internet to work , just simple 900mhz radios. Please visit the offical Meshtastic site for more info https://meshtastic.org
Below are a few interesting videos that demonstrate Meshtastic and its uses.