Hello JackieC,
I had a look at the product you were asking about. It looks like it uses an infrared LED to send information back to the receiver. As it is, it would probably be just like using a TV remote as a IR pen, the IR LED would flash rapidly. The Wiimote Whiteboard did not work when I tried it with a TV remote.
The device could be modified, I do not know how easy it would be. It would involve some soldering, possibly cutting circuit board tracks and adding a resistor to get one of the buttons to turn the IR LED on. After these mods it would probably work well, but it might be difficult to even get to the circuit board.
It would be possible to modify a sensor bar to make an IR pen, but you would destroy your sensor bar in the process. I was impressed by the IR pen shown by
http://undcon.com/mods/irpen/ which looks fairly simple to make.
Regards,
Jason