I have a SitePlayer, and I have to say, it's pretty cool. 8 GPIO lines can be very useful, but 14 could be even cooler. Pricewise, this BS-based thing is a little much, though ($100 for the dev kit plus one unit, compared to $250 for a bulky system). You could mux 256 digital inputs onto the 8 lines on the SitePlayer, if you wanted.
But anyway... Jnadke, while the BS1 and BS2 (no modifier) run on PIC16C57's (I believe), all of the other BS2s (SX, E, PE, P, and whatever else they have) are based on Scenix MCUs. It probably wouldn't be too hard to implement a TCP/IP stack for it, though.
Heh, try writing the entire system for a BS. I dare ya.
PS. Just FYI, I am not a big fan of Parallax, in general.