The PhoneBook - of course.

It's a small MacBook that uses the iPhone as the touchpad and for its radios. There is an app that displays the iPhone screen on the larger display. The PhoneBook runs regular MacOSX so all regular Mac apps work and all iPhone apps work, too.

Connectivity in the PhoneBook complements what is in the iPhone, and there are slots for 16MB+ SD cards to expand storage.

You can undock the iPhone to use it when you don't want or need the functionality of the entire PhoneBook.