You've perfectly discribed the system that already exists. There's a WF app, and there's also a page in the Amazon App that offers the QR Code. Sometimes the sc

You've perfectly discribed the system that already exists. There's a WF app, and there's also a page in the Amazon App that offers the QR Code. Sometimes the scanners installed on the customer side of the POS don't work, so the cashier has to scan it manually. Personally I love being asked if I have a prime account, because they only ask when I haven't already scanned my code, which is something I want to do.