I hadn't realized quite how many of the special-paper-free digital pens were out there now - last time I'd looked, the pens needed special paper and used a pen-tip camera for sensing (basically a special-purpose optical mouse).

Here's a collection of them: http://digital-pen-review.toptenreviews.com/

Interestingly, the last three pens in the comparison table all do look very similar to Wacom's offering. I wonder whether the Wacom pen is using the same technology (or is maybe even made by the same manufacturer behind the scenes?)

In any case, I reckon the Wacom name will help them sell, possibly helping promote them to artists wanting to sketch on the move rather than (as the linked comparison mentions) for business purposes.