Last weekend, I was at a used books shop. I saw a guy with some iphone app, checking the price of each and every book in the shop (there were lots of books for $1). The store people noticed, but didn't say anything, at least I didn't see them say anything. I bet they weren't happy about it.

How long before we just place an order, online, in a centralized place, and pick one of these:

cheapest

fastest delivery

highest quality

or some combination of these, and the app finds the best place to order (amazon, walmart etc) and automatically places the order?