I gotta stop reading forums at 5 am in the morning
I'll be brief and full this in later with better explanations
1) Very cool service. Fast . Quick. Fairly stable
2) Addons are sandboxed with no access to the outside world. They can only see the saved variables folder.
So any file exchange that way is right out.
I'ld suggest some kind of system where you get a really long token that you copy from the webpage then paste in game into an addon. This addon will then process that token or encoded string to present the same sort of thing you see on scribble maps.
With no file exchanging necessary