Here's a nifty hardware project: Handmade Intercom Using Vintage Phones and Buzzer DIY. The idea is that hard wiring up a pair of vintage (push button?) phones requires little more than telephone cord and a 9 volt battery. The creator of the tutorial, Teddy Hashee, shows how a phone line splitter can be used to make the project look especially clean.
The tutorial also sets up a buzzer to simulate a ringer. I find that section of the tutorial to be quite clever as it shows how you can leverage the complexity of the phone without having to understand all the details of it (something I do in programming daily, yet panic and forget to do when dealing with hardware).
The author of the tutorial knocks this project out in 30 minutes. I'm sure it would take a weekend, if not two, for me to pull it off. But when I was done, I would have a point-to-point Bat Phone. How cool would that be? (OK, I don't really have a need for such a thing. When Shira needs my attention, depending on distance and urgency, yelling or placing a cell phone call usually works just fine.)
Here, watch the tutorial: