Sound files.
You can modify the sound files that are played upon door opening, activation etc. Just replace the .mp3 files in the sound_files folder with your own desired file. You can also edit the scripts to play a new .mp3 file.

Amazon Echo.
To enable voice-command functionality with Amazon Echo, please see this tutorial.

GPIO pins.
If you would like to use different GPIO pins for the data cables, you can modify this in the /home/pi/433Utils/RPi_utils/RFsniffer.cpp file for the receiver and the /home/pi/433Utils/RPi_utils/codesend.cpp file for the transmitter, modifying the phrase 'int PIN = X'. Please refer to http://pi4j.com/pins/model-b-plus.html for these WiringPi pin numbers (the bolded black numbers; same for RPI B+ and RPI 3). After modifying this, you need to save the file and type make to compile these scripts, which are coded in C.

The customizability of this security system is endless. All you have to do is edit the code!!