A couple apps I use a lot are the Rand McNally RV GPS and WunderMap. I realize these aren't necessarily the kind of apps you were asking about, but I've found them incredibly helpful while traveling.
The Rand McNally app allows me to enter height information on the RV and it will plot a route that avoids low clearance bridges, etc. This is on an iPad that I use as my GPS (mounted to a holder on the dash). Works great and the size of the screen is much better (and larger) than any GPS I know of. Lot of points of interest, including RV parks and campgrounds, gas stations, hospitals, etc. Downside is that is was expensive for an app ($99), but still less than a traditional GPS. A potential downside is that I can't tell if the map is updating from time to time.
I like WunderMap because I can view wind speeds in addition to rain/snow and temperatures along the route. My very first trip with our FR3 took me along I-80 in winds of 30+ mph. As a new driver, I didn't even think about the effect of wind on the coach. I got blown all over the road and couldn't stop due to a time constraint. Now, I look for the wind conditions and can plan the trip accordingly. It's a free app.
Jay & Jane (Jazzy and Jewel, too)
2014 FR3 30DS
Twin Cities, MN