The directions there are completely useful for anything except something that is intended to be shipped built-in to a phone.
If you want to make your own version of one of the system apps, you need to give it a different package name so you are actually writing a DIFFERENT application. Once you do that, the user can install your app like any other app, and the system will prompt the user to use it in the places it is an option. (And they can drag your icon on to the home screen to replace the one for the standard app.)
--
Dianne Hackborn
Android framework engineer
hac...@android.comNote: please don't send private questions to me, as I don't have time to provide private support. All such questions should be posted on public forums, where I and others can see and answer them.