This project is still in its early stages. Most documentation is far from finished (or coherent), and the code might not work as expected.
A Raspberry Pi operated doorbell.
The project consists of a relatively simple hardware layout, and a RPi.
It uses Firebase for push notifications and to store settings of the doorbell, so that multiple outputs can be enabled/disabled (e.g. you can silence the gong in the house but still receive a push notification).
The .gitignore file that we use in this project is generated by http://www.gitignore.io. Once in a while, they update their data, so it is wise to re-generate the .gitignore by doing:
wget https://www.gitignore.io/api/node,intellij --output-document=.gitignore