Thanks for the replies:
Jez, you said you've tried to use TCP/IP on an 8051 before but you needed find out how they worked to port them to 8051 code. I already have an understanding of TCP/IP and how it works, I just don't want to have to go near the code. What kind of problems did you run into?
In an ideal world, I'd just put the TCP/IP code on the 8051 and not worry about it again ;)

Steve, I'd like to do this with 802.11(even though TCP/IP could become a problem) but thanks for the suggestion. Using serial wireless communication would possibly be easier but I'd like a neat little package when I'm finished.
I'll probably write the PDA software myself too.

My main worries are really getting the TCP/IP stack working and getting a micro web-server going too.

Thanks,
Andrew