Real Time Interactive Map of the Parisian subway system, which includes traffic stats, allows you to plan your intinerary accordinly and etc. A important tool for a crowded and conjested old city such as Paris, where the public transportation is between the most efficient in the world and vital to its economy.
Cellphones sort of being used as GPS units to map the use of city spaces has been explored here.
The electronic maps of cellphone usage were overlaid with geographic and city street maps to produce real time electronic landscapes of the city.
Opportunities for new approaches to city planning and transportation via new urban studies facilitated by technology arise.