Can you give an example of a useful or unusual functionality that can be implemented in this project?

In an iOS project, you can implement features such as interactive notifications with quick reply or actions directly from the notification, which will improve UX.

Another interesting example is using ARKit for augmented reality, allowing users to interact with virtual objects in the real world.

You can also add a feature for automatic saving of the application's state when transitioning to the background, so the user can continue working without losing data.