Smart doorbells can snap a photo of whoever rings the bell, making it so you can screen all those visitors you get throughout the day. Over on Instructables, Naran shows you how to build one with a Raspberry Pi.
The project here uses the Pi alongside an old webcam, breadboard and a button. There's also an optional door-opening push button and Philips Hue integration if you're interested. Otherwise, you'll basically set up the Pi using a special operating system called Prota, wire everything together, then hook the system into Telegram to send you the photos. You'll find everything you need and the guide over at Instructables.
DIY smart home doorbell for less than $40 [Instructables]