Laurent, this is more a direct message to you, but also a pointer for anyone wondering.
I spent about 2 hours trying to work out an elegant way of accessing the Resources directory when building an app with Xcode 4, only to realise Laurent had already included this helper function in the Xcode 4 templates.
So anyone who comes across the same problem you just need to
#include "ResourcePath.hpp"
and then you can load images etc like so
Texture.LoadFromFile(ResourcePath() + "Background.png")
By the way Laurent, your helper function is much more elegant than
Ogre3D's version of the same thing