This is a great concept video by Pam Briggs & Patrick Olivier about 'Biometric Demons', which I first saw when they presented it at alt.chi. It's an excellent example of concept work specifying function without pinning down form. Lovely.
The Biometric Daemon describes a kind of electronic pet that thrives on the biometric properties of its user and which can be used for authentication and identity management. It is based on the novels of Philip Pullman.
The concept was developed by Pam Briggs (Northumbria University - PaCT Lab) and Patrick Olivier (Newcastle University - Culture Lab) - with a PDF link to the scientific paper here: