Some of these GSM modems have AT-commands to upload & run sophisticated, persistent LUA scripts. (Scripts that can can make tcpip connections over GSM, communicate to host hardware via I2C or uart, send SMSs, etc). The possibilities are wide ranging, using officially supported features; no hacking necessary.
Also used in voting machines which "aren't connected to the internet" (!)
e.g. https://freedom-to-tinker.com/2018/02/22/are-voting-machine-...
Some of these GSM modems have AT-commands to upload & run sophisticated, persistent LUA scripts. (Scripts that can can make tcpip connections over GSM, communicate to host hardware via I2C or uart, send SMSs, etc). The possibilities are wide ranging, using officially supported features; no hacking necessary.
see: https://simcom.ee/documents/SIM5320/simcom_lua_application_n...