I don't see the privacy issue here. They're just measuring physical activity per quadrant. They can use it to study which products and product areas seem to be attracting the most interest. They specifically don't use photography or wifi that follows people around.

Although the vibration/light sensors are a somewhat novel idea, in the end a retailer already knows exactly what products are sold, in what quantities, which ones are returned, and (anecdotally at least) which ones spark the most questions from shoppers. It's not long in coming before UHF RFID chips will show the products being carried around the store (or out the back door, etc.).

Probably this system would be most useful for determining which products are "hot" and should be moved to an end cap or special display near the entrance. Or they might choose to "bury" the products to force shoppers to walk past tempting tangential items.

Retailing is a science, perfected over many decades. The lights, the music, even the aromas, all conspire to influence shoppers in ways that online can't compete with. I wonder if retail in fact will eventually find a formula to outcompete the online folks. (I'm still kicking myself for ordering a Pi Zero W online when I could have driven the same day to the Microcenter and picked one up.)