It's possible to send additional properties from the app to the server-side application. This can be done with Start request. But it's also possible to send parameters from the server-side application to the app. This can be done directly in server-side application as usual with JVx'.

Here's an example:

getLauncher().setParameter(IMobileConstants.PREFIX_CLIENT + "apiKey", "12345");

The app will receive a specific response:

{
  "name" : "applicationParameters",
  "apiKey" : "1234",
}

All custom properties are available in the app automatically.