Want to sound a buzzer every time someone walks in a room? Snap a power module to a motion trigger module, snap the motion trigger to the buzzer module, and you’re done. Want to light an LED ...

Here is an ultra simple Arduino Night Alarm project wired around a handful of inexpensive and easily available components. One advantage of using Arduino as a security system is the flexibility!

You'll need an Arduino along with a bunch of various sensors to get the project rolling, and once it's all set up you'll have a simple, but cheap system to monitor your home.