This product and its cousins explain Apple's extreme focus on miniaturization and thinness. Two iPhone generations from now (6S) the processor, display, and battery tech will be sufficiently advanced to also make an iWatch, iPocket Watch, or iPendant practical. Some form of in ear bonefone mic and speaker is likely to be important to the project. With a watch on your wrist you can speak into it and even hear audio, but by then HD audio and noise cancellation will be an expectation, which is why a bonefone or in ear device is more likely. Another optional interface may be a glasses frame system. Hence Google's focus on that layer. It will certainly be LTE data only.
Rocketman
Rocketman