When I was young, and had just started out in my software-development career 20 years ago, I wrote a little bit of code on my Amiga that took a password, but also recorded (within some threshold), the speed at which each letter of a password was typed.

This meant that, not only did the user have to type in the right password, they also had to time the key-presses.  To test it, I'd have a rhythm in my head and could consistently re-type the password every time.  However if I just typed it out regularly, or slowly, it was not accepted.

I am no security expert (my programming lies in less-difficult areas, thankfully), but I just suddenly thought about that program I wrote when I was young and whether it was a viable addition to security these days, or whether it's not even worth thinking about.

Tap - Taptaptap - TapTap -- Tap.

The term you are looking for is "keystroke dynamics" or "keystroke biometrics" and is an interesting and growing field. 

The idea is that an individual types certain keys in a certain way that does not change much over time. If you can map those dynamics, then you could, potentially, do away with passwords altogether and simply get the user to type anything. 
