He decided to go with the low-cost SIM800L GSM modem, but as it only works on 2G networks, provisions have been made in the board design to swap it out for a more modern module should you desire.

Real Time Home Security System using GSM Technology-An Anti-theft System ... which will initiate a telephone call when push button switch S2 is activated by the user (or by another electronic module).

The SPCN310.000 GSM module can be assigned to any mobile network by the insertion of a standard SIM card. The modem is compatible with the complete range of SPC panels and plugs directly on the main ...

This tasty proof-of-concept cellular sandwich is made by adding a Sim900 GSM/GPRS module, which communicates via UART, to the Pi/TFT hardware while using a piece of foam core board in the middle ...