I used to work for Zenith back in '96 and we tried to recognize logins by the way people typed. It successfully recognized when I logged in with just my left, right or both hands. There was a problem though. Good typists type fast. Because of that, good typist filled the keyboard buffer and the software saw them all good typists as typing at the same speed. Looks like keyboard buffers are faster now. We were using a lightning fast 16MHz 386 at the time. Ah, the memories of starting a compile overnight and it not being finished when you come in the next morning.
Some times I sit and think and sometimes I just sit.