I recently read a paper describing a touch screen interface on the body of a steering wheel with the use of a webcam, projector, Wii remote(used for the driving simulation) and some acrylic glass. I thought it was interesting to see another approach at limiting distraction while driving, besides that of what Project54 is doing.
As you can see below, the acrylic glass was used as the body of the steering wheel while the projector placed an image on the glass, a webcam recorded any gestures made by the user. In this prototype, the camera and projector are attached to a rotatable stand which allows the projection to move with the rotation of the steering wheel. Later studies may find whether or not this is the most optimal solution (projection could also be fixed in one position so it does not rotate).
In the experiment itself, users were asked to create gestures on the glass for specific tasks using their thumbs such as playing a song or starting the navigation system. Many of the users used similar gestures and also transferred gestures they knew from other touch screen devices (iPhone etc.).
Since this is an early study, there seem to be many faults with this approach. I believe that memorizing gestures may be unappealing to many users and even the ability of creating your own is, or could become, annoying. Also, if the entire body of the steering wheel is used by this projection, then the gauges (speedometer, fuel and temperature levels) would need to be relocated as well.
Although it may have its issues, as any early research does, having an interface on the steering wheel may be a great solution to limiting distraction while driving!