My apartment building has an old-school analog doorbell system. Using some small components, a Raspberry Pi Zero W and a bit of Python I was able to digitalize my doorbell. I recieve pushover notifications when someone rings the doorbell. Ideal for when my music is on 100% or if I'm not at home and can alert a roommate so he or she can open the door for a delivery.
This specific schematic is designed specifically for my own apartment. It is however possible that this schematic will work for your own use case. My doorbell is an oscillating electromagnet, but as long as your doorbell makes an electric circuit when someone rings the bell it should work.
This Python script was created for the Raspberry Pi Zero W running on Debian/Raspbian 9 (stretch).
git clone https://github.com/lesander/doorbell.git
cd doorbell/
pip install -r requirements.txt
cd ../
python3 doorbellI make use of pm2 to transform the Python script to a daemon. For this to work you'll need node and npm.
npm install pm2
sudo pm2 startup systemd -u pi --hp /home/pi
pm2 start python3 doorbell
pm2 save