garageCube

What remote control options do I have for the video player, when I have to play the movie inside a room, and the PC is in a control room?

Any wall button options?
Any App for an Android tablet?
Any control processor?

You can use TouchOSC, it's available for iOS and Android. It allows driving all controllable parameters of MadMapper with a custom user interface (buttons, sliders etc). There are a bunch of other options, Touch OSC is popular and reliable: https://hexler.net/touchosc