Apple has patented the idea of using a mobile device "to acquire pricing information for a shopping list of products," which basically sounds like an official version of SnapTell Explorer -- point the camera at something and then get a list of available prices for it. But this patent goes a step beyond that. It also suggests that a "mobile device" user could scan a full list of products, and then possibly even buy them directly from the phone. I imagine that's something like walking around a grocery store, scanning items as they go in your cart, and then checking out wirelessly from your phone.
We've seen a "pay-by-phone" system in place before, but this sounds like a much larger system. And of course, security concerns would come along with it, so it'll probably be a while before you use your phone to check out in a major store. Still, even though there are lots of Apple patents coming down the pike that might never actually get implemented, I'd much rather deal with my phone than a line and a surly cashier.