I had a question from a customer as they were working through the process of configuring the infrastructure for the mobile companion apps that are available for Dynamics AX. The trick with these application is the authentication i.e how do you know the user that is using the mobile app is allowed to log onto your ERP application.
This requires a reasonable knowledge of active directory, networking and Azure to make the choices for your environment. If you want to do some reading here are some links to get you started.
This whitepaper gives you are run down of the specific configuration that is needed
If you want to know more about the development of your own applications and more technical details about how the Dynamics AX mobile apps communicate then this white paper is very good for the developer folks.
The Azure service bus acts is that relay between the mobile app and your on-premise system. You probably want to get familiar with how this works.
There are some infrastructure pieces that you might want to have some background knowledge of like Active Directory Federation Services (ADFS) and a component of that called ADFS Proxy. These are needed to allow those mobile users be authenticated.