Cool! I think a cool idea for a related service would be crowdsourced local price comparison. Take pictures of items in store with an app, which uploads to your servers to do OCR/mturk and get the UPC. In exchange, users get coupons. Then when they want to buy an item, they go to your website to find the store selling it for the cheapest.
It would add accountability to the claims by big retail chains that they "match any price."
