UK-based FoneJackerHacker, consisting of person or persons going by the moniker "M Booth," has truly put the "retro" into "retrofit" by modifying a 1940's-style rotary telephone receiver to now serve as a unique iPhone docking station/speakerphone system. The dock is mounted in the handset cradle, and in addition to two speakers in the handset proper, a third speaker resides behind the dial. Promises Booth, "I am working on a version that has a microphone on the handset and with
the use of an iPhone .app that I am developing you will be able to use
this as a handset for the iPhone, or as a headset."
Here's the inevitable YouTube video of the contraption in action:
(Did somebody just yell "ALBATROSS"?)