One of those little robots might follow you around a grocery store, perhaps second-guessing whether you should buy that bag of chips. Or, the store could use a checkout-free system announced by Y-Combinator startup Standard Cognition. Shoppers sign in with a mobile app and then the system uses machine vision to watch what they put in their carts and charges them automatically when they leave the store with it. The system also alerts store staff if someone tries to leave without paying. Whether that staff is human or robotic, who knows?