Thanks for the link. That blew my mind! I wish it could be added would, my phone would replace my scanner instantly.
I've been using CamScanner on Android since forever. I only stopped a few months ago because I moved to iOS (and didn't realize it's also there).
It does the page detection fairly well, but also let's you correct it. Very useful, specially when the picture is bad. I then used to upload it to Dropbox.
This could be done server side if you're already doing ocr.