In this video we build a very useful intruder alert using Arduino. The project is very easy to build and the cost of it is very low. All you need is an Arduino Uno, a GSM shield, a PIR sensor, and a DS3231 rear time clock. You can buy all these parts from the links below. The project, when it detects motion, it sends an SMS to a predefined telephone number! That’s a great project to build and protect your belongings!