Office Lens is a Windows Phone app that does the following:
- Straightens images taken at an angle
- Auto-crops the important part of the image
- Shows what will be cropped before the image is taken
- Removes glare and shadows
Before there even was Office Lens, the de-facto app for this sort of thing on Android and iOS systems has been CamScanner for some time. It does exactly the sorts of things you're talking about here. There are quite a number of similar apps as well, but that is the one I've seen used by folks for this job.
Besides your requirements about auto-crop and perspective fixes, it also handles OCR and other document archival related tasks. These might actually make the app more cumbersome than useful to you, but there you have it.
