Let's first see what we need for this project. Apart from the usual Arduino Uno board, you will need XBee modules, both for Arduino and your computer. Here is the Arduino board with an XBee shield mounted on it, along with one XBee module:

As your computer doesn't come with built-in XBee, you will need a module on your computer to communicate with the Arduino project via XBee. To do so, I used an USB XBee explorer module from SparkFun, along with an XBee module mounted on it:

Note that for this chapter, you can also use a Bluetooth module to interface your Arduino board with your computer, without any major change in the code.

Finally, you will also need one or many motion sensors. I used a simple PIR motion sensor for this project; you can find this sensor on many resellers' websites. The most important point here is that the sensor should be compatible with the Arduino Uno voltage levels, that is, the sensor should have a maximum voltage output of 5V.

This...