These days most of the mobile applications are consuming rest based api only for their contents and pages because it is always better to manage one site instead of two different.
So your application also should not be an exception of it. As aem provides rich mechanism to expose its content to third party with the help of Sling model exporter, experience fragment and path based sling servlet so you can take help from these to accomplish your task.
Since most of the sites are using scene7 for their digital assets, that also become a path for you to use rest based api from aem and consume in your app.
For extra security purpose you can use some api management tool if required.
Hope this will help.
Umesh Thakur