In the real world, banks and other traditionally early adopters of security solutions have been using hand-geometry readers and other biometric devices in operational environments for decades. Law enforcement has used biometric-based security just as long. Each requires special equipment. For example, voice recognition calls for a microphone and a PC sound card. For face recognition, you need a digital camera.
All biometric technologies work in roughly the same way.
This lets the system build a meaningful set of biometric attributes into a template for later matching. The biometric system is later used for identification or verification. Often leveraged by law enforcement, the identification is labor-intensive, requiring that the system compare a new sample with all possible candidates. In this case, the software looks up the template related to the user name, compares the new sample against it and determines if it has a match. Of course, biometrics are not 100 percent accurate.