Sounds "tempting". But I am nearing the first year (Nov 30th) of my cell phone use. I was only convinced to carry one because I carry. Then less than half a year later I got the Stinger, and my Bluetooth capable ZTE flip phone paired with my Stinger perfectly. I don't need any stinkin' "smartphone". NAV is a luxury. Without it, I'd simply go back to plotting my trip the night before with Google Maps, and following my own directions (with the satellite view in my head). NAV works well enough for a first experience with onboard navigation tech.
In the not too distant future, all of this variance will be moot: all onboard systems will be hooked into a virtual, 3D view of reality anyway: actually showing the immediate future as you approach your next turn off or direction change: with real-time video of the actual place, not some computer graphics model. Everything we are using today will look as quaint as 19th century illustrations by comparison.