Inspired by this thread, I added a ‘smart’ door sensor to my dumb wired doorbell without other electronics or wiring.
The catch is the doorbell has to be using electromagnet to ring the bell so the reed switch of the sensor will be triggered when doorbell button is pushed. If you have the digital kind that play different ring tones, I image it’s still possible to wire a electromagnet to it for this purpose.
The door sensor behaves like a momentarily switch sensor, shows “off/close” when the button is pushed and then switch back to “on/open” after 1 second or so (bell done ringing).
Also, since our doorbell has front and back door buttons which ring different bells (i.e. 2 electromagnets), I’ll be adjusting the sensor position so it will be triggered by both buttons.
If you have the electromagnet-style doorbell like mine, give it a try, find the magnet(s) inside the bell housing and place the sensor as close to it as possible, that’s it. Remember to set up automation/trigger like for a momentarily sensor.