@foone one of my older phones (one of the Samsung Galaxy ones, but I can't recall which) had an NFC chipset where you could get it to present an arbitrary UID, although you needed to sideload an APK to make it work because the original app got taken off the store. was useful though. I used to store hotel keys on it because most of them in that era just used the UID and didn't do any actual cryptographic handshake.