I’ve just released OATHAuth 0.1 for MediaWiki. This is an HMAC based One Time Password (HOTP) implementation providing two factor authentication. This is the same technology used for Google’s two-factor authentication.
OATHAuth is an opt-in feature that adds more security accounts in a wiki. It provides two-factor authentication, using your phone as the something you have, and your username/password as the something you know. If you are using iPhone or Android, you can use the Google Authenticator app as a client. There are also clients for most other phones and desktops; Wikipedia has a good list of clients.