monkeysphere user command should be able to import existing ssh keys as OpenPGP subkeys
Similar to how monkeysphere-host has an import-key function, so should monkeysphere have an import-subkey function, that would take your existing ssh key (~/.ssh/id_rsa for instance) and import it as an authentication-capable subkey to your existing OpenPGP primary key.
(from redmine: created on 2009-03-07)