Generalized transactions

We use different services like ticket reservation, vehicle booking, booking at service-station, movie tickets and many more. We do all this either through web or mobile-phones. Each of provide a specific service. Hence for different services we have to interact and deal with different parties.

If we have an integrated central party which can act as a mediator between customer and service providers, it will be beneficial for all. Customer now has to interact with a single application which will further route the request to actual service-provider.

But How? .... Valuable suggestions welcomed