A camera works fine, FWIW. It's all integrated at API level. Some supermarkets here let you use your phone (and could take payment further, to remove the physical checkout process), and others use handheld scanners which could also integrate with phones for checkout (direct NFC payment, or scan a barcode on your phone to upload your cart, pay for it).

So many options, such glacial movement.

https://smartshop.sainsburys.co.uk/ https://secure.tesco.com/clubcard/scan-as-you-shop