Fitts' Law is very curious. It is a model of human movement which predicts the time to move a mouse/cursor/etc to a certain target area. The work for this was done back in 1954, and has many implications for design then as well as modern and future design.
The way humans move has not changed for years, and will not change quickly. What this law tells us is that in designing new interfaces, we need to be aware of the time it takes for a person to find and select an icon. This time can affect how well the user likes the program. So, when designing an interface, one should be aware of the size of their icons and buttons, since it could influence how users like and/or enjoy the program/device.
