That's exactly what KeoPass[1] does: a biometric key (your fingerprint), that behaves like a no-driver-needed USB dongle/keyboard.
Your grandpa could use it to secure his crypto wallet.
Your grandpa could use it to secure his crypto wallet.
For a certain sense of "secure". Because fingerprints aren't. Not just because you leave them everywhere, but because the way we examine fingerprints doesn't have a result that is particularly unique.
Not even at the criminal case-law level [0][1].
That fingerprints are unique is an assumption, but it doesn't match our reality. They're useful for eliminating from a known small pool, not matching against a large group.
Many of the elements we match against run in families.
[0] https://mccoll-law.com/attorney-profile/37-general/38-finger...
[1] https://www.telegraph.co.uk/science/2016/03/14/why-your-fing...