: Uses Bluetooth to create a mesh network that works at concerts, sports events, or during emergencies. While primarily for messaging, it can reach recipients over large distances by "hopping" through other users' phones.
Making calls on Android without Wi-Fi is possible through several specialized technologies, ranging from offline mesh networks for local communication to apps that utilize traditional phone lines instead of data. Offline "Mesh" Calling & Messaging Calling Apps For Android Without Wifi
: Features a "call routing" option that uses your wireless provider's voice minutes instead of Wi-Fi or data, which is useful in areas with poor internet coverage. : Uses Bluetooth to create a mesh network