Take a look at some "sophisticated" retinal scan, they are in the end cameras, a special kind one. Fingerprint readers? Another kind of scanner. It doesn't matt

Take a look at some "sophisticated" retinal scan, they are in the end cameras, a special kind one. Fingerprint readers? Another kind of scanner. It doesn't matter that today's only few simpler model can be cracked with a single strip of scotch, it's only a matter of time. And we can go up, even imaging quick DNA scanner, quick enough and smart, it does not change that much, your DNA can be grabbed around you in many way. The essential point is simple: using your body means using an exposed key, using a password means using your brain that it's far harder to "expose". Also passwords are trivial enough, you can even check your keyboard for builtin keylogger, protect your environment from camera, microphone (phone/audio analyze to determine key's you press) etc. Try to hw check a biometric system and well... Good luck.