Will this automatically center and apply perspective transforms to pictures taken with phone cameras?
It also doesn't tie you to a specific ecosystem.
Disclaimer: I'm on of the authors of Genius Scan :)
Most documents I do want to keep record of are sensitive. I don't trust a closed-source app with that kind of information.
To unwarp photos that were taken at odd angles you need to do some image processing. The mathematics aren't particularly difficult, it's a homography transform in most cases (rectangles). The problem is robustly detecting the page.
Dropbox has some nice write-ups on this: https://blogs.dropbox.com/tech/2016/08/fast-document-rectifi...
This could be done server side if you're already doing ocr.
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.