There's also some discussion at this page that references something called ARToolKit (Sourceforge project page) which can use the EyeToy.
If someone could compile up the necessary drivers/software to use the EyeToy via USB on the 6k, that would be pretty slick. The Zaurus + the EyeToy wouldn't be the smallest or best portable digital video camera available, but it's free if you've got the parts... Like I do