Dry erase board lined with IR sensors to record pen strokes [video]
My high school had these in 1995. Each marker color had a different reflective pattern on a band around the tip so the scanning laser could read it like a bar code. I remember the eraser having a solid reflective band all the way around. It was pretty cool, as we all got whiteboard "transcripts" emailed to us at the end of the class that you could play back / pause / rewind / etc... whenever you wanted.Also, these boards had no projectors (they used real ink in the markers) and didn't require special markers (just the barcoded pen collars, which were removable)