Think of the back button on Safari, press/hold to see a list previous pages loaded. ios-multi-back-button by Anders Borum follows the same line of thinking to display a list of view-controllers, allowing a user to go back multiple levels without the typical tap-tap-tap.
“Users long-tap the back-button to display a table with the viewControllers in the current navigation stack. They either lift the finger and tap a table-cell or move it above the table and release above the cell for the view-controller you want to navigate to. If they do a regular tap, the back-button will bring you back a single level as usual.”