Best Buy started doing this with their app. I’ve used it multiple times already. It’s so convenient. Scan the barcode with your camera in the app, it adds to the cart, pay when you’re done.

Anecdotal experience: Unfortunately, products that are locked up create a problem. I went in for two items. One of which was a single RAM stick for laptops. The employee refused to give me it even though I was literally going to pay for it on the spot as I had already collected the other item I wanted. He insisted it goes to the register per policy. I quickly got the barcode as he held it, then paid. “There. Paid for. See” as I showed him the screen. Dude was so annoyed as he handed me the RAM.