Meshtastic-Android

Meshtastic-Android is the phone app for a mesh network that runs on cheap LoRa radios and needs no cell service, no carrier and no internet. You pair a radio over Bluetooth and get encrypted text messaging, position sharing and telemetry across a mesh that relays through every other node in range, which is why it gets used for hiking, off-grid property, disaster response and events where the cell towers are saturated. GPL-3.0, and there is also a Compose Desktop build.

The app is the easy part. Install from GitHub releases (pair with Obtainium for auto-updates) or from the store; the `fdroid` flavor drops the Google Crashlytics and Maps dependencies if you want nothing phoning home. The actual work is the hardware and the firmware, which lives in a separate repository. Recent additions include mesh network discovery, waypoint geofences that alert when nodes cross a zone, encrypted backup of device security keys, NFC contact sharing, XEdDSA packet signing indicators and air-quality telemetry.

Free, no tiers, no accounts, backed by The Document Foundation model of an open collective rather than a company. The money goes to radios: a usable LoRa node runs roughly $25 to $60, and you need at least two.

The catch is bandwidth. LoRa is measured in bytes per second, not megabits. Text and coordinates work. Anything resembling a photo, a voice note or a web page does not, and no amount of app polish changes the physics.