I recently got interested in APRS - Automatic Packet Reporting System. Commonly used by radio amateurs for vehicle tracking, APRS has many other features which make it ideal for real-time situational awareness. In particular, fixed stations may use APRS to beacon information such as weather conditions; repeater identification, location, and status; station status; messages to other users, and many other things. Additionally, mobile users can use devices such as the HamHUD to view this information. Some devices even plot users' locations on a map!
