Regarding your request for Apps, the single best that we use is GasBuddy. Once I have planned our route using Rand McNally GPS/GS trips (and after getting DW's approval :-) ), I use GasBuddy to find the best price of fuel. If I am unsure about accessibility, I use Google Maps (Google Earth and Street View) to check physical layout. All the while trying to avoid getting into a place I cannot get out of without unhooking our toad.
Another website that is useful if looking just for truck stops is
https://www.truckstops.com/.
Hope that helps.