http://www.israel21c.org/bin/en.jsp?enDispWho=Articles^l2158&enPage=BlankPage&enDisplay=view&enDispWhat=object&enVersion=0&enZone=Technology Maybe I've seen too many movies, but if you wanted to fool the system you could kidnap the person with clearance, film his eye-movement pattern, and create a program to copy the eye movements and use that to program a mechanical eye in a robot. Highly sophisticated, of course, but plausible isn't it?
I have heard that such "biometric" devices are having such loopholes exposed, so dont toss out the old lock and keys just yet Cool though, they did something similar to this in Oceans 13-a limited AI that read peoples eye movements and was thus able to detect cheaters and sharks, because people expecting to win all had similar eye movement patterns.