The biometric daemon was proposed in a 2008 paper (PDF) by Pam Briggs and Patrick Oliver, and it’s a very clever thought-experiment for a user-centered, adaptive authentication system. The idea is that the daemon, a cuddly toy, (the name is inspired by the Philip Pullman Dark Materials novels) knows a bunch of your biometrics (fingerprints, voice, gait, etc), and uses them to verify your identity before logging you into various services (ATMs, online services, mobile phones).
Biometric daemons: adaptive authentication via electronic pets – Boing Boing click through for a link to the full paper.