Taxi services are a centuries-old profitable business model (London had first laws regulating "taxis" in the 1600s).

Dispatch via app is a solid improvement over the old phonecalls or street pickup, automatic credit card billing is an improvement over cash, and in cities with shady taxi drivers, GPS tracking is an improvement over potentially hacked taxi meters.

So there is an obviously valuable business model for "taxi dispatch app" here even without a moonshot - just perhaps smaller than Uber's dream of being the only provider of personal transportation in the world.