And in fact a friend of mine and I even debated this as an early internet business back in the 90s, though nothing came of it. However, such a business has to start off competing with a the monopoly fleet which its legal advantage, so it has an initial hurdle that would not be there in a free market. But indeed, I think something like this will probably be how it starts. To compete with the hailing system, you need a large fleet to draw on so you can get somebody a cab as quickly. Ideally drivers and cab companies would transmit their location and willingness to take a fare through the network to a database, where any dispatcher they are contracted with can grab them and allocate them to the customer, transmitting a photo of the customer and their location to the screen in the cab.