With two flipper zero, perhaps linked by bluetooth, you could have one as an NFC reader and one as an NFC card and allow a “man in the middle” log of all NFC data exchanged and store on the SD.
That’s not MiM that’s a relay attack. The sub GHz radio might be a better option because of range limitation in BT.
Ah, well, I was considering for diagnostics where range would not be an issue. Many protocol specs seem hard to get even when the protocol is not really vulnerable to attack, and a diagnostic of a card/reader interaction would be helpful.
But yes, it could be used as a relay attack.