It is better to create small modular apps instead of single monolithic application. In Bahmni EMR we have small apps for Patient Registration, Consultation, etc. An end to end functional test covering patient registration and consultation goes through multiple apps. We needed to abstract the concept of an app in test code to increase the readability and maintainability.
The app objects are natural extension of page objects recommended for writing functional tests. An app encapsulates all pages and coarse level actions in the app.