Quite some time ago, in the early 1960s, Ivan Sutherland developed an interactive sketching system. Even if you do not consider the bulky house-size computers of the time, Sketchpad remains a remarkable milestone in HCI. Here is a short clip out of a seminar by Alan Kay "Doing with Images Makes Symbols. Communicating with Computers"(Apple 1987) where he comments on Sketchpad:

 Now please fast forward by 46 years an watch what's possible today:

Amazing, isn't it? (Source: IxDA-discuss)