This tutorial shows you how to create an intruder alarm that sends you text message alerts when motion is detected. This may sound complicated but I am pretty confident any beginner with electronics should be able to do this just fine. The range sensor senses motion and tells your Arduino board to send the text (SMS). So you can leave the intruder detector at home, connected to your network, and still receive the SMS alerts, no matter where you are, as long as you have cell phone service.
This is a pretty quick and easy project, it takes maybe 45 min.