hey jf3000... when we go touring, 2up and towing a trailer (or towing a van with our car), we use -
FuelMap (we like like to refuel every 300ks or so)
Where is Public Toilet 1.20 (tells you how far away the next one is... also they're usually situated in a town park, which makes a good rest area too)
Google Maps
I know they're books and not apps, but we also carry a caravaning camps and truckies atlas (not the same book, strangely enough)... cheers, John & Kate.