I'd assume the sensors can do a couple things - sense your proximity to your goods (the closest) and sense the difference in time between when you leave and whe

I'd assume the sensors can do a couple things - sense your proximity to your goods (the closest) and sense the difference in time between when you leave and when your goods leave (the smallest). I'd also assume that they use logic along the lines of "your goods are those which have been closest to you (and not on the shelf) for the most time since you entered the store. I'd assume trying to forcibly enter the store without registration will set off an alarm. I can't wait to show up with 15 of my friends and run amok in the store - it'll present an interesting legal experiment (unless they just get us for trespassing).