They are correct. What you need to look into is AJAX/JSON and how to present your data to your app using these technologies.
Expression Engine would actually be quite a good choice for this as its template system is quite flexible. There are even add-on modules for delivering your content as JSON if you want t go that route.
A quick google led me to: http://samcroft.co.uk/2011/updated-loading-data-in-phonegap-using-jquery-1-5/
It's a bit more than you need since you will have your content in an existing CMS instead of creating a new database to store the data, but the concepts will hold true and I am sure you will be able to use it to find more tutorials that suit you better.