Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I believe it was introduced (previewed) sometime last summer, shipped in December 2007.

The ugliest thing ive ever seen. If Apple is going to make a <i>real</i> tablet I'll put money down that it won't ship with a pen.
 
It's a modified MB, that allows the user to interact with the OS and programs using a stylus instead of a mouse. They've been around for a while, although I've never seen the MB version until now. I've only seen the MBP version (I think).

I'm sure there are people who find this very useful, and would prefer not to have to use a tablet PC, or attached Wacom tablet to get the functions.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.