Have an extra PC but no monitor? Use VNC to control it. It's less expensive than a monitor, easy to use, and saves space. (A great way of checking in on the kiddos as well. ;)). VNC can also be used to control your PC from your cellphone, and vice versa on a rooted phone. RealVNC offers this service with good performance and low memory usage on a LAN. There are plenty of third-party client/server programs freely available for Windows, Mac, and Linux, and newer Windows versions have a built-in RPC utility that can be controlled from other programs as well. I have used M$'s RPC version on a few occasions, but I still prefer third-party VNC applications. It's is easy to setup on a LAN, a bit more trouble if you intend to use it over the internet. Everyone with a network should have VNC installed on their machines and accessible from their computer. It's so much easier when the kids yell "Mom!" or "Dad! My computer is messing up again!". You will be glad you did.
I found a few Youtube videos that show how to configure and setup my Windows favs, RealVNC and TightVNC, and a demo of VNC on a smartphone. Setting this up is a breeze and well worth it.
For Linux, I recommend the Remmina client coupled with "Remote Desktop" server for Linux distros. These are installed from the package manager and configured in much the same way. Remmina has the ability to handle both VNC and RPC servers. I love it.
Here are the videos:
