I have a compact flash gps, with my Dell Axim pocket pc. The external antena sits on the dash, and is very reliable. Got it on ebay for €100 new. You might want to consider that, as it's a big saveing over a blue tooth, if you don't mind the wire.
I don't know how intensively you intend to use your gps, or how much reliance you intend to place on the info it gives you (not starting a debate on that one!), but you might consider pocket fms, instead of Anywhere map. It's free (give a donation), and I think it's just brilliant .
http://www.pocketfms.com/
It has a lot of features, although given that it doesn't have the backing of big corporation, I am not inclined to trust stuff such as frequencies! However, you might as well try it, before forking out for the anywhere map, if may be sufficient for your needs.
Also consider a suction mount to hold your pocket pc in place when flying. (Passengers have a tendency to drop it
)
Having never used another gps, I'm not too sure if it's the same for all gps solutions, but I find that a pocket pc based one is strictly for setting up on the ground. Tapping screen and setting up flight plans, going to diversions etc is just far too fiddly to try to do in the air. Everything needs to be set up in the calm of terra ferma. Maybe this is the same for all gps solutions.
Hope this helps!