@ingrid not sure if this is in the scope, but a uni friend and I once built a pedestrian navigation system for Daimler. It was serving mobile phone users in Berlin using WAP and was deployed at IBM in ca. 2000. The navigation data came from some XML-based API provided by Daimler and was targeting cars IIRC, so had to be “translated” for pedestrians. I remember some headaches recognising roundabouts because Daimler’s API would serve those as multiple right turns in a row…