Randy Murray on his recent visit to the Apple Store:
And then I remembered the new Apple Store iPhone app. I pulled out my iPhone and downloaded the app right there on the spot, using the Apple Store’s wifi. I opened the app and it recognized that I was in an Apple Store. It let me scan the barcode on the product, confirm the purchase using my iTunes account, and showed me the receipt. I asked a passing Red Shirt if that was all I needed to do and he smiled and said, “Yep, you’re good.” So I put the adapter in my pocket and walked out of the store.
Haven’t had a chance to try this myself yet, but it sounds pretty awesome.