Software that can interpret sketches as input (e.g. a circuit diagram)

The original Apple Newton Messagpad did this for basic shapes. It worked much better than the handwriting recognition.

To erase a shape, you simply scribbled it out.

Unfortunately it interprets everything as a circuit diagram.

the system can recall the direction in which the stylus was moving when a particular stroke was made

Shooting white-boards or sheets of paper with a phone cam is probably more convenient than scribbling on a screen, but that requirement ...