This is an improved version of my previous offering, http://www.thingiverse.com/thing:369475. The improvement is a simpler script from the point of view of the user. Only phone dimensions need be defined and all the rest is calculated. As a bonus I also cut out unneeded material saving both material and printing time. To create the STL file you need to customize the Python script and execute it within FreeCAD. Customizing is simply measuring the dimension of your phone (with protective case where used) and editing the Python script. You also need to state the pathname of the STL that is created. FreeCAD is an Open Source modelling toolset available for all popular platforms, Windows, Linux and Mac. Get it from http://www.freecadweb.org/wiki/index.php?title=Getting_started.