pay by palm and the ugly mess of tap to pay

WSJ: Cash, Plastic or Hand? Amazon Envisions Paying With a Wave. Articles linking to WSJ coverage say it might be no-touch:

A patent application dated Dec. 26, 2019 from Amazon Technologies, the company’s Mumbai-based electronic manufacturing arm, for a “non-contact biometric identification system,” describes a hand scanner, which can capture images of users’ palms with wrinkles and “deeper characteristics” like veins.

It reminds me what a stupid mess the tap-to-pay rollout has been in the USA, and how it has left the door for new solutions even wider than it would be otherwise. The problem with tap Point of Sale systems is multifold:

1. Many places don't accept tap. Or I've seen some where they have a tablet rigged up as Point of Sale device with a magnetic strip reader, and they support tap but it's a separate dongle they have to haul out.
2. The iconography that "tap is available" is unclear, and often the "tap target zone" isn't clearly marked, and I don't think there's a single above screen/below screen standard.
3. The UIs sometimes have a weird wait before they're ready to go... the system needs to be in a certain state to receive the tap, which is bad enough if sort of understandable, but then the UI isn't making the procedure clear for the user.

(To be fair, "3." is an issue for chipreaders and swipe systems as well... it's ridiculous how many places make the customer play the "can I do it now?" games. It's challenging because even if when the information to wait is clear on screen, no one reads screens. Maybe some kind of universal iconography, like a green/red light -- except in the shape of a tape recorder stop/go symbol so it's colorblind friendly? Ideally there might be a physical forcing function, but that might be more expensive or prone to breaking down...)

Come to think of it- I just realized I think of tap-to-pay as a virtual wallet on phone thing, but that's not the case- I guess my cards could have a little soundwave/speaker/wifi-like logo on them if they could be used, but they don't. Still - ambiguity reigns with these things.

Of course "Wave to Pay"... it reminds me of that old Hitchhilker's Guide Line where the salesman/priest/spokesman says "Now, let us all bow our heads in payment..." I love how prescient Douglas Adams was about gesture systems in general...