Definition of biometric is;
Biometric verification is any means by which a person can be uniquely identified by evaluating one or more distinguishing biological traits. Unique identifiers include fingerprints, hand geometry, earlobe geometry, retina and iris patterns, voice waves, DNA, and signatures.
Biometric security devices are pretty high up on the security ladder, as far as controlling who has access. (See the Security Ladder post on the Security Blog). New devices are being introduced at a rapid pace, and as a result are becoming much more affordable.