The circuit is highly-flexible so that you can use any SIM900A modem (and ofcourse any Arduino Uno board) of your choice. Carefully read the modem documentation before construction to make the task ...

Arduino MKR IOT Bundle: There is a slew of Arduinos you can choose from. But for most home automation decisions, the is a great option and affordable ($89 at Amazon).

The system uses both an Arduino and a Raspberry Pi alongside a ton of various sensors to monitor the house. You can set up the system to send you alerts when something happens or just monitor ...