Agreed that this would have to be a smart vision system that can scan the barcode, and maybe the shelves are attached to a scale to determine weight of items as

Agreed that this would have to be a smart vision system that can scan the barcode, and maybe the shelves are attached to a scale to determine weight of items as they are placed back in. With that information you could determine size of a jar of mayo along with its current weight to estimate amount of mayo remaining. Meats and vegetables would still be a challenge though, but perhaps object recognition could help with that. Fridges are already overpriced for what even the fancy ones can offer, I imagine we're not there yet to incorporate multi-camera vision systems with beefy AI processors at commodity prices yet.