I used my Pocket PC on our last trip. All trip planning info (PS times / confirmation numbers, etc.) was stored in a single Excel workbook that I could view on my Dell Axim.
There is a site called pocketdisney.com that has park maps and other utils.
I also found another site that had iSilo content related to WDW. Included were the show times (updated via a partnership with Steve Soars' site), restaurant menus (again via a partnership with Allearsnet.com) and other trip planning info.
The menus were great. There were a couple of times DW and I started discussing where to eat, and I was able to produce current restaurant menus without trekking all over the park. Don't have the link to this site handy, but if anyone wants it, just PM me and I'll dig it up. I believe there was a one-time charge of $8, and the content is updated weekly.
Wireless access is available at a couple of resorts, but don't get too excited about it. The cost is high. The coverage area is very limited (common areas of the resort). And, if you want the in-room high-speed Internet, the two products are priced independently of one another.
The beauty of a PDA is that you can download everything you need before leaving home, thus eliminating the need for realtime access in many situations.