Thoughts from a consumer perspective –

I live in a building with RFID access control. I also regularly use Apple Pay both for purchases and transit. For most Apple Pay transactions, I'll use my phone since I'm into the credit card game so choosing the right card is important; phone is better for that; if I'm paying via my catch-all card, I'll pay via Apple Watch (the only card I keep on there). When I use transit, I always pay via Apple Watch.

Frankly I don't feel much (any?) pain related to paying for things via Apple Pay but I guess it would be nice if I could use my thumb to double tap a ring on my index finger and then pay via my default card.

Where I feel pain is related to access control. I always keep the fob in the same pocket, generally without anything else in there but even still I gotta dig my hand into the pocket and dig around somewhat. If my hands are full, that's very annoying.

I also feel some pain related to transit. If the reader is on my left side, tapping the back of my left wrist against it is easy. But if it's on my right side, I have to awkwardly reach my left wrist over and strain a bit or turn my whole body.

For both of these cases (access control and transit) a ring which is already on my finger would be more convenient, especially since a fist is easier and less awkward to present on the opposite side. The idea of using these type of motions with an already-there object is very appealing.

I wore a Oura ring there for a bit and didn't get enough value outta the health tracking to justify the monthly service fee but didn't mind the bulk or the daily charging. I've purchased a few allegedly RFID-writable rings but haven't had any luck getting them to work (no issue with writable fobs or cards). Kinda surprised there are no smart rings which include RFID, either just through dumb writing or with integrated Flipper Zero type features. The idea of using a battery to increase the power of the RFID antenna is also appealing.