Ha, that's a great idea. Partition purchases by hour, figure out which products are bought disproportionately often in particular hours, and for the top three of those products, Kiva their shelves either to the front of the store (if you want to optimize for greatest throughput) or the back of the store (to optimize for longest time-in-store to increase impulse buys) ;)

Oh god, "Now where did the bread aisle move itself to today?"

My guess is that its a mixture of indoor position tracking of your phone and infrared/computer vision for the products that detect a product being taken.