I have a few suggestions to the current app.
First could you add a click or sound or vibration when a picture has been taken.
Second is in the magic window it would be great to see the picture for transcribing after the picture was taken. It would also be nice to zoom in and pan to read things better.
It would be nice to be able to use the zoom lens on my phone because sometimes it is hard to keep your shadow of of the markers at close range. I do realize that would make it tougher to get an accurate GPS mark using a zoom lens. Maybe you could add a button to mark the GPS location while you stand next to the grave and then step away to shoot your picture, zoomed or normal. That way you can get a more accurate GPS and better pictures.