As I mentioned before, we will be using a Bluetooth module to communicate with the Arduino. The specific model is the HC-06 module, which is one of the cheapest Arduino communications modules and is widely used. We could just try to hook it up to our smart phone and send an alert directly to it, but what if you aren't at home? That is a drawback of using Bluetooth.
But fret not. We will capitalize on what we can do using just the Bluetooth. I think this is a good time to explain the plan before diving into the details.
The following is a representation of what we are going to achieve in this part of the chapter.
We use the PIR sensor ...