One of the most awesomely useful devices I ever saw was a pen-input version of this. It was used for teaching in a software testing class. It had the slides on it, and the instructor could annotate the slides in real-time and, if she wished, save the annotations for the next class. It was, of course, repeated on a projector.It inspired my lifelong desire (well, all my life since them) for the ultimate smartboard. Full-color e-paper, markers, erasers, and the ability to save the screen to a thumb drive and bring the same one (or a copy) up later, halfway across the country, and continue working on it. I've seen school smartboards, but the closest that I've seen to my perfect device requires a spare room next to the conference room for the rear-projector. A front projector would have peoples' shadows.