FacilMap is a privacy-friendly, open-source versatile online map that combines different services based on OpenStreetMap and makes it easy to find places, plan trips and add markers, lines and routes to custom maps with live collaboration.
Detect how far off route the user is. If the distance exceeds a certain threshold (50/100 meters?), add two via points: one for the last known point on the route, one for the current location.
Indicate the already passed part of the route in a different colour
Show the distance/time/arrival to the next/final destination
Depends on #275.
Add a way to “start” a route: