Q:

Focus engine tvOS

I have searched on google and found a couple of example for tvOS focus engine.  does this tvOS feature work on iPhone or iPad?  
Can a user interact with touch instead of apple remote on iPhone or iPad? 

A:

The tvOS focus engine only works for tvOS devices, like the Apple TV, and the feature does not work for iPhones or iPads. 
Yes, the user interacts using touch on iPhone and iPad (iOS devices) instead of the Apple remote. 

From the App Programming Guide for tvOS

On iOS devices, a user interacts directly with the touchscreen.  On Apple TV, a remote is used to control the interface indirectly.