A short note on how to use the Digital Input port on the Maestro 100 GSM Module
The I/O port input is available on the 4 pin cluster on the serial side of the modem.
You should make the wiring as according to the above diagram.
Then first you can AT+WIOW=2,0 (disable output function)
Then you can read the input port value by AT+WIOR=3
Try to open and close the switch and see the return value change