Build an app or program

I'm building a hologram pyramid and I would like to develop a program or app the allows users to insert their own footage in to a template that looks like this video - [login to view URL] - but I would like to improve on it a bit (e.g. like implementing a shared screen kinda thing where the user basically uses his/her other devise normally but is projected onto another device where the screen is split like the video linked. the main important part is the thing about inserting the user's own footage.