Excellent if your phone is in a case or skin (or without).  These mounts are what you need so that your back seat passengers can watch movies or play games.  Great for keeping the kids occupied during those long trips.

Don't confuse this mount with those that use velcro straps.  These clamp securely onto the metal posts that support your headrest.  Your phone sits within a an expandable cradle.  Installation and removal can be done in a matter of seconds.  

These mounts support your device in portrait mode as shown.

Take a look at these pictures.  We're going outside to watch a movie.  You can too after buying this mount!