In the past when I got calls in the car, I'd have to take the phone out of it's holder and hold it to my head if I wanted any kind of clarity. I didn't like fiddling with this, so I recently purchased some adapters that allow me to hear phone calls out of my car speakers and talk to the person on the line with an external microphone. Not satisfied with most of the external car microphone offerings available, I purchased the recently released Rode Videomic ME, which is a sort of "boom" microphone for your phone, and used some adapters and extension cables to mount it in my car. It even has a "dead-cat" for wind protection, and the option to add a second microphone for a passenger!
Dave Burt is a career audio engineer and is currently working as a freelance Production Sound Mixer.