I have this goofy promotional pen from CEDIA, handed out at WALC 2006. It is made of clear polycarbonate (?) and has what I thought was a goofy feature: an LED hidden inside that illuminates, mostly, the area around the pen point on the paper.
It wasn't until I tried to take notes on an Ecuadorean intercity bus at night that I saw the point, so to speak. There were no reading ights on the bus (or rather, they were disabled), so I needed a handheld light to write. The illuminated pen solved this problem more conveniently and more energy-efficiently than a separate flashlight in the other hand. The only goofy thing about the feature is that the light is blue (hard to focus on and hurts visibility of blue ink from other pens) rather than red (saves night vision, more efficient). But you could also put a little mouse camera near the end to watch unevennesses in the paper go by in order to digitize each stroke for later uploading, like Anoto without the pricey paper, and the LED can serve for data sending and receiving to other devices as well as visible signaling. With a small electronically-controlled valve in the pen cartridge, you could do virtual invisible ink: turn the pen on when it's going over areas you want to color in --- and get a means of graphic output without the expense of a display.
