I have the Garmin GPS app on my Focus and recently tried to use it on a 800+ mile road trip. I ran into problems that I cant explain. The phone kept indicating GPS signal lost at various times and often would not re-establish contact for long periods. (clear skies, no trees etc) This, of course, stopped the navigation functions. I've done this exact same trip with a real Garmin device and had no troubles with GPS signal etc. One thing I noticed is that I was usually in-between towns or near very small towns when this happened. Possibly with little or no cellular service. Do our phones require a cell signal (and/or data) in order for GPS to work? I dont see why they would but it sure seemed that way on this trip.