iOverlander - lots of wild camping spots reviewed, has feature filters, app works offline, near useless without paid subscription, which is absurdly expensive
park4night - lots of wild camping spots reviewed, has feature filters, app works offline, near useless without paid subscription, but price is reasonable
searchforsites - works offline, has feature filters, provides data in KML/CSV/OV2 format, mobile app requires subscription, but price is reasonable
Truckfly - database of truck stops, free, has feature filters