On my last tour I loaded my route into Ride with GPS and used a RAM mount to hold the phone. Ram Mounts are a total overkill, I don't even try to debate that point. However, it held my phone and gave no trouble at all.

I then fed power, continuously, to the phone from a solar panel. At that point, it really was as simple as following the line. It also provided a location update, every ten minutes (adjustable), so my wife could see what I was doing.