Secondary System For My Phone

So I saw this (www.google.com.sg/amp/www.theverge.com/platform/amp/circuitbreaker/2016/7/22/12257358/haimawan-mesuit-case-iphone-android-os-app)
online and I thought, surely it's possible with android too.. right? It's basically an iphone case running android that uses the iPhone as a screen.

I'm thinking of doing something like that for my galaxy s5. Perhaps I can connect one of those android sticks to my phone. But the problem is.. how? Is there an app that displays a hdmi input on the phone, or streams from another android to my phone? (something like teamviewer or splashtop, but through a cable). Or maybe I maybe I have to build the phone myself? (no idea how to, but it will be a cool project)

The reason I want to have another system is so that I can switch to and from it easily. It also for Pokemon Go, so I don't have to worry about SafetyNet blocking it, while keeping all my mods on my main phone. (installing/installing Xposed everytime I want to play pokego is driving me crazy)

If nothing works, I guess dual booting is also an option... but that's not fun.

— modified on Oct 13, 2016, 3:34:23 PM