The WSJ did an interesting piece about making a custom phone while working with Chinese manufacturers directly: http://www.wsj.com/video/how-to-build-your-own-smartphone-for-70/90013EB1-9BB0-4AE8-9BBB-FE76793EAD30.html
Also, this article reminds me of the prank / hoax video showing people how to add a headphone port with just a drill 
