I’m not sure if I’d personally call this a robotic pen but it does have the cool factor of a really smooth but slow opening cassette deck (remember those).

Squeeze the button and - in a curiously slow motion which is much of the charm - the pen mechanism unfolds, presenting you with a full sized biro. When you have finished, simply fold the pen up again.

There is a video of it in action which since my recent problematic Vista upgrade I am unable to watch (or play any sound to that matter).

You can get the “some what robotic pen” from Grand Illusions for £3.95 (~$8).