Random thought: What about using a pen instead of a mouse?

It occurred to me today: What device have people historically used to provide them with a high degree of pointing accuracy? A pencil, or a pen. And that's what a mouse does: It gives a person a high degree of pointing accuracy.

Given that a pen is something people learn to use in school (even previous generations are great at it), I'm surprised that this hasn't been used more.

Now, pen interfaces already exist... artists use them for drawing on the computer, etc. But if I'm not mistaken, you have to also hold the pen up to a special surface. I wonder what this technology might be like if you didn't have to hold the pen up to a special surface, and it still worked if then pen came a little off whatever surface you held it against.

Does it afford more or less accuracy than a mouse? What would it be like using a computer with this device for clicking on icons, dragging windows, etc.