That said, this isn't an entirely unique concept, and you're right, positioning the camera is challenging. There are tools to help with this--arms and stands that position devices at the correct height to photograph a standard-sized sheet of paper. It may strike you as entirely impractical, but I remember the days when scanners were huge and bulky things, and even now when they aren't, I don't necessarily have the desk space to keep one out, or the desire to hook it up and store it when not in use. A reliable camera-based OCR solution for my Android phone and an arm/paper guide calibrated to the S III would rock, and assuming reasonable material prices and standard markup (I.e. not the absolutely huge markups of AT) it'd be competitive with dedicated OCR solutions and hardware.
Source: I'm blind.