I have used Cachemate on my older Pocket PC. I have a Pharos GPS that plugs into the CF slot on the top which made the unit the ideal, all in one geocaching tool. I could search for the closest cache, read the entire description with logs and press the goto button and follow the arrow. The biggest problem was the lack of ruggedness. A good jar would reset the thing to factory default settings and erase the memory.
If I could find a rugged enough Pocket PC with a built in GPS and WiFi, and the price was right, I would definitly get it.