On a recent tour my NOAA Hi-Def Radar app was very helpful. I could swipe the screen to look ahead of my route for ugly weather and adjust accordingly. The satellite maps are very high resolution.
I gather that some versions use Google maps and some Apple maps but developers say their goal is to be using Google's vastly superior maps. It's not a terribly important distinction because you're looking at huge distances.
As a vegetarian I found the Happy Cow app of limited usefulness for eating on the road. Using the location feature of the phone it's supposed to identify vegetarian restaurants in the area. It was okay in larger urban areas but about useless in smaller communities. Also, the rating system is pretty rigid, making it even less useful in the sticks.