For a long time, MIT had in its lab software that, from freehand figure drawn on a screen, perform recognition and conversion to software for geometrical accurate data.
In addition the software recognizes symbols of electronics and can recognize a diagram or drawing of circuit. And also chemical symbols from which it can reproduce the molecules.
But he lacked material for public use. With iPad and other PC tablets, or smartphones, the hardware is now available.
As you can see, a simple pencil whose movements on a touch screen are recognized by the software is enough to write on the surface like on a magic slate.
We could imagine this software installed on the Samsung Galaxy Note (clic below on the video). This smartphone allows to draw on the screen with a stylus so easily and so smoothly that one does with a pencil on paper. Its software has a recognition of shapes since the video shows that it correct forms to make them regular.
However the MIT's software is designed to run on Windows and contains .dll files. It is the same for the free software Sketchboard that uses the mouse to draw shapes.