What similar things do people use now?
Those fields are actually built a bit deeply into SMF for some reason, so it's not completely trivial to change, but it can be done. Low on my to-do list, though, as hugeblack mentioned.
Ive long thought there should be a spot for PGP fingerprint.
PGP fingerprints are SHA-1, which is insecure. The OpenPGP standard really needs a complete new revision...