When we consider functionality within any application, we should always come back to the outlining question:
Many designers take the approach in thinking the answer is achieved with innovative layouts, big, bright buttons or loud, bold text. We know the real answer simply comes down to consistency. Without consistency, we simply create confusion.
Remember, mobile apps are used on daily basis, and the user is not limited to only your own apps appearance and disciplines. Humans work in patterns and based on previous behaviours, we make predictions of what to expect when we next interact with similar functionality.
Mobile apps are native to the device and because of this, common functionality is built right into foundation of operating system. Therefore, if we take the correct approach, creating consistency in our apps should come with minimal effort. Understanding the operating system and standard functionality is essential before designing apps. Look at how the disciplines within the built-in iPhone iOS apps are consistent throughout.
Having a good understanding of the consistency in the iOS standards, such as system provided controls, icons and layouts, means we can begin to take these external consistencies which work across different apps and integrate into our own apps, presenting familiar behaviours and allow the user to identify key functionality easily.
As we are no doubt going to add our own branding, icon styles and colour scheme, the consistency becomes ever more important, UI elements must behave in the manner the user would expect and the navigation must flow in harmony to corresponding apps.
Below is World Cup Prediction App for the 2014 Brazil World Cup, created by Apps Plus. The app used common conventions combined with its own style of a south american decorative theme.
If we can adhere to these external consistences then when it comes to adding our own styling and individually, we keep the functionality intact and with a familiar user interface.