One of the interesting use cases the side-shelf integration in Notes 8.5 has is a cross page wire function. This option allows for a side-shelf component to be shown in the side shelf the entire time a composite app is open (not just visible or the active application). When a property is published from the side-shelf component to a component on the main screen area the system will automatically show that components page (perspective) and deliver the data to the target action.
In this video I show a basic example where I put the PIM contacts in the right side-shelf. The component is configured to always show while the application is open. Every time an entry is selected in that view, it publishes properties to a web form. That web form lives on the second page in a composite application and will be shown every time I click an entry.
There can be many other uses for this kind of technology. For instance, a basic navigator that will always open a specific page in a composite. Or one where it not only opens a page but does a search on the data published in an application.