Sam's Club does this now. You scan on the mobile app while you shop, then pay right there on the app. It's great.
You can also do this at Walmart (with Walmart+), though you still need to stop at the self checkout on the way out to get a receipt. It's pretty handy. I wish Costco would adopt this too.
I agree, and if you bring bags with you, you can bag as you scan. Works great for quick shopping trips, not so much when I'm making a big purchase.
I am just a few minutes walk from my local grocery store, so I go frequently. Rarely use a cart, just my canvas bag. Will there be portable scanners, or will I have to drag a cart around to benefit from real time scanning?