Localization, Internationalization extention

I will love to see an extention to allow me to work with multiple languages, say Spanish, English, German or other languages. I been looking around for tips and tutorials, ideas & howto's but no one seems to put everything together or have it work with Dreamweaver. In a globalize world, developing or building website in only one language may not be enough.

What I will love to see on it is:

- Determine the folder where language files are. One file for each language.
- Type of files to maintain the information, php, xml, plain text or others.
- Have a list of language variables for each of the translations so I can keep track of new additions if I add new text.
- Automatic modification of headers so it can include the proper html encryption.
- db dependant or not.
- Ability to choose between sessions, cookies,.., http-vars.
- Autocheck if a language variable is in use, where or how often.
- Have a default language.
- Auto apply session_start();, or whatever the server model is, to new or created document(s)

This extention will really be a great time saver.