A fingerprint sensor isn't possible, appreciated, but what about a U2F activation button? It could even just be a wireless pass-through for USB to allow your yubikey to work for example (I'm certain this can be done on Linux but unsure about other oses)
> It could even just be a wireless pass-through for USB to allow your yubikey to work for example
Everyone would be better served with a generic USB hub in the keyboard, not shipping a security key with the keyboard.
https://github.com/zimengxiong/tinytouch spoofs as a card reader but won't work with Apple Pay and the like.