My good friend Jamie Sharp sent me this link today. It's amazing: watch how Adam and Jamie easily defeat a fingerprint lock the manufacturer claims has never been broken. As if to snub the claims, they break it three times! Supposedly it monitors pulse, sweat, temperature, and other attributes. First, Adam obtains an impression of a fingerprint already present on the reader and creates a latex copy that he adheres to his own thumb. Initial attempts fail, but when Adam licks the latex, the door opens. Next, Jamie tries a ballistics gel copy of the fingerprint. Sure enough, the door opens right away. Adam remarks that some cheap computer fingerprint reader was actually more difficult to hack than the "unbreakable" door lock! Finally, Adam tries the simplest of all attacks: a photocopy of the authorized fingerprint. No warmth, no pulse, only a lick -- and again, the door opens.
Biometrics is identity, not authentication. Authentication requires a secret of some kind, like a PIN or password. Anything you leave behind, like the fingerprint Adam lifted from the reader, can never be used as a secret, and thus can't be considered authentication.