I used this as a pilot program in Pittsburgh when I lived there. It was a hand scanner running some sort of Android based OS but largely the same thing. You scan your store card to unlock a scanner, scan your stuff as you walk through the store putting things in bags, then you walk to a kiosk, pay, then walk out.

I used to get so many dirty looks from people who thought I was stealing a whole cart of groceries until they saw the receipt print out.

Doing it directly via an app would have been even better!