What about a smart shopping cart that close a lid when you pass the checkout area and then somehow figure out whats inside. After you cross the pay area it will open if you paid for everything
Uniqlo does this - they have RFID tags embedded in their products so you can just dump all of it in a special basket at checkout and it autodetects everything. I suspect they also work for anti-theft as there are no separate, bulky anti-theft tags to remove.