Using HC-05 to play a sound on an app
Every time the Arduino detects motion, I want a sound to be played on the phone of the person with the app. In order to do this, I plan on using a HC-05 Bluetooth Module.
Does anyone have any suggestions for how I should build the circuit and what code I should use?

The Arduino sketch above is a good start.
The first step is to connect the Bluetooth module so that the Serial output can be sent. The circuit is simply connecting the Bluetooth module to RX/TX on the Arduino. I am assuming that you have written an app that can read from Bluetooth on the phone and write to the screen.
The second step is to parse the output and play the sound. That is also part of the app and not the code on the Arduino. To make this easier the sketch output statements can be changed to something easier to parse (detect).
All and all the work is mainly app programming.
Cheers!