App creation - very large project

We need an app which will probably be 2 apps. One needs to to be for the provider of services that needs to include a diary system, messaging system etc. the other needs to be a client app that contacts to the provider of choice through maybe a unique pin number, they will need to be able to see and request dates and times from the providers diary.

This needs to be developed across all platforms iApp, android etc.

This is a very brief outline and we don't know if it is possible to have 2 different apps that link via selection of the provider.

Regards
Ian