Since one of the tabs/sections is "Text" that allows you to enter text, I'm guessing that the text will be displayed on a LED sign/display.
So, I do have a lot of experience with LED signs and their protocols (Cpower, Translux, Glare, AMS, Optec, etc), but I am curious when you say that a "file" is send from the device to the app to describe the UI.
Obviously, I am familiar with routers and ipcam devices providing a "portal" that a browser can log into them to adjust their settings, etc. But you seem to be describing something different.
So I have some questions:
1) Does the "file" just dictate the UI elements and the app needs to figure out their layout/position?
2) Are you basically looking for an app that will display the UI elements in a very eye candy fashion to impress the user?
3) When the user interacts with a UI element, how and when is that action sent to the device?
-John