Quantity   Component name
1 × Raspberry Pi Any other device with UART capable to run Python will do, too
1 × SIM800L GSM Modem Any other modem using AT commands via UART should do, too
1 × Supercapacitor, e.g 1.0F 5.5V Buffering the extra power potentially needed during high RF activity spikes
1 × RGB LED w/ resistors (optional) Used for some status indication