Distance & GPS
External service (Google Maps, Mapbox, OSRM) that computes real driving distance and time.
A routing API takes origin and destination (and optional waypoints) and returns real driving distance, estimated time, and route geometry. Providers: Google Maps Directions, Mapbox Directions, OSRM (open-source), HERE, TomTom. Typical paid cost: US$5/1,000 calls. Mileage apps wrap this call and return the result formatted into the receipt.