Pick a Finger, Any Finger
Fingerprints: With a long history in law enforcement and government, fingerprints are the most widely researched and understood biometric. With relatively high accuracy, low price and minimal intrusiveness, they are also by far the most popular biometric for use in business and enterprise solutions. Individual fingerprint scanners typically cost between $100 and $150.
Iris Recognition: Iris scanners use video cameras and sophisticated targeting software to isolate and identify complex patterns contained in the iris of the eye. Patented by Iridian Technologies Inc., iris recognition offers probably the highest available accuracy and low intrusiveness (no physical contact is necessary) but at a relatively high price.
Retina Scanning: Largely overshadowed by other technologies, retina scanners use a laser to illuminate the interior of the eye and identify patterns in the capillaries on its back wall. Though extremely accurate, retina scanners are highly intrusive, difficult to use, and typically cost $2,000 to $2,500 per unit.
Face Recognition: Face-recognition technologies use a variety of techniques to identify unique or unusual facial features and the distances between them. Though nonintrusive and low cost (typically requiring only a cheap low-resolution video camera), facial-recognition systems offer relatively limited accuracy and may require substantial processing power in a commercial IT environment.
Voice Recognition: Voice-recognition systems are extremely cheap (requiring only the standard microphones built into most modern PCs), are nonintrusive, and can be used over a telephone or other remote voice connection. They offer relatively poor accuracy, however, and are often highly vulnerable to background noise and other environmental factors.