Barada (Barada Aint Respecting Any Deceptive Adversaries) is a PAM module designed to provide two-factor authentication support. There is companion software called Gort which runs on Android devices, essentially turning your phone into a SecureID token.
The PAM module is available in the repositories for Debian based distributions.
Gort, the Android client, is available from the android market (https://play.google.com/store/apps/details?id=net.sf.crypt.gort)
Awesome project for securifreaks