I came up with an idea for this app! Scan the items in, keeps your total, but alas...I was told that each store has it's own prices for the same sku, so it wouldn't work unless it was proprietary for each store. The problem with that is that the store doesn't want you to quit shopping, so they don't really want to help us out!
They have apps that all you do is enter either the names of the items on your grocery list & The store you want to shop at & it will give you the prices to each item & your total. The app also has the options to scan the items in by running their bar code across your iPhones screen or you can enter the items in or scan them in & google will instantly give you a list of stores that sell the items starting with the store selling the item for the lowest price.