Apple recently filed for a patent that would allow the iPhone to be “locked down” using a fingerprint or even a vein pattern, as opposed to the more conventional keypad currently found on the iPhone. As I am sure you are well aware, entering passwords on the iPhone, or even unlocking the device using the keypad gets to be quite cumbersome after a while, to say the least.
This new technology, currently under development, would allow iPhone users to prevent unauthorized access to their entire device, or even to just specific parts of it.
How exactly does this work you ask? Apple is proposing that a small sensor would be hidden within the device, or that a sensor currently found on the iPhone would be modified (via either software or hardware) to accommodate this.
Apple has even gone so far as suggesting DNA recognition! While this is certainly not feasible with current technologies, I’m guessing that in at least a decade mind-blowing technology such as this will be the norm.
Another less exciting way of locking down the iPhone proposed by Apple is run of the mill voice-recognition technology that would make use of the iPhone’s internal microphone.

Sun, Mar 29, 2009 | by Tim Bradbury
Rumors, iPhone News