Similar to what the Spotify or Apple Music app does when a song is playing, it places a custom view on top of the UITabBar:
UITa
Since iOS 11 this became a little easier. When you add your view, you can do the following:
viewControllers?.forEach { $0.additionalSafeAreaInsets = UIEdgeInsets( top: 0, left: 0, bottom: yourView.height, right: 0 ) }