This video shows how to build a smart video doorbell device with 2-way audio and iOS push notifications, using a Raspberry Pi.

Here is a list of parts:

Raspberry Pi 3
https://www.adafruit.com/product/3055

MicroSD memory card
https://www.amazon.com/gp/product/B06...

Power supply
https://www.amazon.com/gp/product/B07...

Plastic case
https://www.amazon.com/gp/product/B01...

Video camera module
https://www.amazon.com/gp/product/B01...

Speaker with built-in amplifier
https://www.adafruit.com/product/3885

Mini USB microphone
https://www.adafruit.com/product/3367

Button
https://www.amazon.com/gp/product/B01...

Jumper wires
https://www.adafruit.com/product/1953

And here is the link to the operating system to use on the Raspberry Pi (Raspbian Stretch)
https://downloads.raspberrypi.org/ras...