This button covered gadget is all my mum uses to shop with. She picks it up at the entrance to the store, (the store provides all shoppers with sturdy nylon bags, one of which is thermally fitted) she wanders round the store, and scans each item before putting it in the bags in her cart, and then goes to an unmanned checkout, scans a "stop now" barcode, at an ATM-like machine, pops in a smart card, pin number, and takes the receipt. No intervention by anyone. Waitrose depends on the honesty of their customers. and all she uses are these four UI buttons.