Fingerprint readers, the most popular of biometric devices, have dropped down into the $100 range. Of course, you must also have the computer interface and purchase the software that goes with the reader. Hand geometry, facial geometry and retina scanners are also becoming increasingly affordable.

Finger print readers are the easiest biometric devices to fool, and most of the the other devices can be fooled one way or another, but biometric vendors are working hard to produce "foolproof" models.

A popular option is to use multi-mode devices. The person must present both a body part and an identification card or badge. The card or badge may be contact or proximity (not actually displayed) and carries information about the person's fingerprint. If they don't match, access denied.

Here is a good article at Network World that also has a number of links to related articles.