While shopping apps for smartphones are a dime a dozen, generally there's not much they can do other than give you a list. If you asked us who would be first in line to improve that experience, Nintendo is not a company we'd name, but this patent application for a semi-interactive shopping experience on the DS handheld has us standing corrected.
Here's how the DS shopping app would work: Once you've got all your groceries listed, it would track exactly where those items are once you get to the store via a rather fanciful "in-store wireless shopping network." The DS's dual display would put your list on the right and a layout of the store on the left. Now you can plan your shopping trip to maximize efficiency, never returning to the same aisle twice.
While there might be some merit in an app that lets you map out your shopping this way, I'd be way more interested in an app that would tell me whether or not the store I'm going to is all out of orzo pasta before I get there. Then I wouldn't just be saving time — I'd save gas, too. In any case, since any app like this would need on your local Safeway to be consistent and comprehensive about its inventory, put all that data online, and have a reliable wireless network… well, let's just say Fresh Direct is looking pretty good.