Hello Sir.
I think I can help in your task.
In my job I usually make models as they are in reality, them separate faces, or regions, for applying different materials, for rendering and animation. My renderings are based on these materiais and the shape of the product, and not a image wrapping applying.
You posted a iphone as example, and I have an Iphone rendered too, together in other product.
Feel free to check my portifolio, " Product / Surface / Assemblies Design III " has an Iphone there.
Thanks you for opportunity
Regards and Happy 2014.