Wired doorbells draw power from two wires that are connected to a transformer that steps down your household power to between 16 to 24 volts. If your home is not equipped with doorbell wiring you can wire it yourself using a plug-in transformer, or have an electrician do the work for you. Either way, some drilling will be required to run wires from the inside of your home to an exterior location.
Signal Private Messenger is one of the most popular privacy chat apps. It features end-to-end encryption for all messages, voice calls, and video chats between two Signal users. It focuses a lot on individual chats. There are group chat features, but it's mostly for personal use. This is one of the biggest differences between it and rival privacy chat app Telegram. Video calls worked fine in our testing so we have no trouble recommending them. It's a neat way to get some encrypted chats as well. The app is also completely free and open source. You can't really go wrong with it, but there are better video chat apps if you need group video chats.