Not to rain on your parade. Shoeboxed* does this type of thing already. I am currently using their limited trial. http://www.shoeboxed.com/receipts-for-taxes/ I'm not sure how you would differentiate yourself. You might have in mind other ways to tackle this problem.

You have an excellent idea and the space ripe for disruption because I for one dislike receipt management for expenditures. It is a necessary evil.

*I'm in no associated with any of the above.