Python client for the $20 Colmi R02 smart ring

Is there a similar ring with NFC?

I have no use for the smart health thingies, which really look like a data driven health gimmicks to me.

NFC on the other hand I could find hundreds of applications, from payment to access and transport cards.

Yes. I have the Z1 Ring.

Getting secure tokens (like payment, door unlock, etc) is possible but can be complicated. The ring is a small target, so not always easy to find the received if you're using it with a phone.

Oh, and the software is low level and finickity. I managed to accidentally set mine to read only mode permanently.

Review at https://shkspr.mobi/blog/2024/02/giving-the-finger-to-mfa-a-...

I have a suspicion this is a whitelabeled NFC ring I got from AliExpress for $12. That one includes a T5577 chip and a Mifare tag. You can read and write the Mifare tag with your phone, as normal, and the T5577 with a Flipper Zero or a Proxmark (also from Ali, $40).

The NFC tag is a small target, probably because of the size of the antenna, but the RFID one has pretty good range. I got five of those rings, very much recommended if you have stuff to auth to.

I think your suspicions are wrong. Those $12 rings will allow you to serve NDEF messages or similar. They won't do U2F, payment, car unlock etc.

It doesn't look like the Z1 does payment either, though. I don't know how they do U2F, but it looks like it comes with a custom reader, which is non-standard. I don't know how Tesla unlock works, so I can't say there.