I'm sure not the person of experience when it comes to a combo Pocket PC/GPS combo it just seems to me that if it goes down, you're SOL for LRH.
The alternative route would be to have seperate devices. I went on to Amazon.com and used their search feature
to explore, educate myself and decide on a used iPAQ Pocket PC 2210/2215 model. The only diff between the 2210/2215 is the 2215 is not a retail item, it's a model sold directly to companies. I was able to win a $110 bid plus $7 shipping on Ebay. It even came with a huge "extra" 900 Mhg battery and cradle. It runs EXBAL (same as your Nightforce program, just with the Nightforce logo attached) extremly well.
I would look at the Kestrel comparison page to help decide what model pocket weather meter you want.
You'll need a model which will read temp, wind and Barometric pressure. I believe you want a minimum of the 2500 as it has Baro pressure, which you will definatly need. Humidity does not, as I''ve been lead to believe, make that much of a difference. I just ran my EXBAL, and with the 639 yd shot I made this morning, it's only a .2" difference between 5% and 100% humidity. But it you are anal enough to worry about it, get the 3500 and you'll be set for anything LRH can throw at you.
The only time you'll need altitude is when you set you zero on your rifle 'cause when your out hunting you'll want to enter the exact "station" baro pressure, not the standard pressure. It's more accurate.
Good luck and I hope this helps!