There are many sensors, that can be used with Intel Galileo to create security devices. Let's look at some of them.
There are many motion or passive infrared detection (PIR) sensors available to be used with Intel Galileo. The sensor shown in the following image, manufactured by SeeedStudio, is one of them. Their use is pretty straightforward. All you need to do is connect VCC, Ground, and one GPIO pin for detection output. After you have connected pins, you will read HIGH (1) from the connected GPIO pin; otherwise, you would read LOW (0).
Note
You can find more information about motion sensors from SeeedStudio from the following link: http://www.seeedstudio.com/wiki/PIR_Motion_sensor_module
Motion sensors can be used to develop a device that can sense movement and alert the user. Another use case with energy management is that you can turn on or off a light bulb after a motion has been detected.