I have seen a few YouTube videos of people using IPads to control everything in their home theaters. Lights, projector, bluray player etc. How difficult is that to setup?
Not that difficult, but it kind of depends on what you have to control. Some components have their own iOS or Android app that works on your network, but you'd probably need an app for each one.
You might look at the Harmony Smart Control as it seems to be able to control most things by itself.
Both appear to use a relay device using a smartphone's bluetooth or wifi signal.
I use mine to control it all but my projector because my projector doesn't have an app. The rest of my equipment is new and all has apps that are proving to work quite well......IE no need to pull out the remotes for anything.
I bought an iPad mini and it's a perfect size.