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 ...

He’s using an Arduino Uno and an Ethernet breakout board to hook it up to the network. This allows him to send text messages to himself when the alarm system is armed, disarmed, or triggered.

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!