It is very easy to build an “SMS-controlled relay” with the help of a cheap GSM modem module and a small microcontroller board. Here, I’m using the SIM800L and Arduino Nano V3 to develop a nifty ...

There are 12 connections in total (6×2 rows) on the SIM800L module and, surprisingly, one row contains all of the connections required to interface with a microcontroller like the venerable Arduino!