Are you using this CONUS or OCONUS? I know my new phone has GPS in it with all kinds of features that makes a Garmin all but obsolete. Baring the the usual - no 3G service, poor coverage, battery life (But I have a
Solio solar powered charger that works fairly well.) Or the SHTF situations - IE Skynet, 2012, EMP's, Happy Tree Friends, etc. My new phone is pretty much an all in one, I could get rid of my Camera, IPOD, TOM-TOM, Garmin, etc provided everything is working as planned.
That being said I don't think I would be calling CAS with my smart-phone even if I were CONUS. It's just as important to know a systems limitations as it is to know how to use it. I own an old Garmin, but one of my Team Leaders had the 401 mounted on his buttstock, he would simply cant the weapon get his bearing and keep on trucking. Always worked without any issues and he loved it.
SOS