The Path 2.0 iPhone app (http://path.com) uses an expandable menu to free up some extra real estate. The Path app places a button in the lower left corner of the screen. When the user presses the button, menu items expand out from behind the button in a circular pattern at a fixed distance from the main button. To close the menu the user either selects one of the options presented or presses the main button again.
The following is a quick overview of how I implemented a navigation system similar to the Path iPhone App.