Are you using the GPS for hiking? For driving navigation, I'd prefer a dedicated device. Navigating by phone works generally, but (1) it can be awkward to operate since the phone isn't designed for that; and (2) the reception may not be as good or as accurate as a dedicated GPS.

Like you, I also worry about putting all my eggs in one basket. If your cell phone fails or run out of juice, you may not know where you are, and you cannot call for help.

Da Bing