I know NWA allows is above 10K feet and pilots have the ultimate discretion. I pull it out, if they ask I show, if they question I point them to the section in their flight handbook that says I can. Never had to escalate beyond that.

I have it built into my BB 8800, I just kill the cell phone service and use it as a handheld GPS. Usually get 4-8 sats strong. I get a kick out of it

Granted my 8800 you have to know where you'll be going since you'll need to "trace" your route when you are on the ground with cell service and cache the maps, you can't just download and store maps to your phone yet