
It CAN work, but one of the main factors is the quality of the microphone. The store sell
this one, which is $330. I see there is another one for $60 but not sure about that.
The issues in the car is the type of noise changes, so you can't just train the computer to ignore the noises. It's louder at higher speeds and very different when the windows are open or the stereo is playing.
You may not the Microsoft Sync product uses a button you push to tell the computer when to listen. That's a good start, but I'll bet you can tune that system to the individual car. You need to do that for the Mac, but I'm not aware of how to do it.
Voice is cool -when it works. But there are lots of reasons it doesn't in the car environment.