The so called TDS, or technological distraction syndrome, is a widely spread topic of research and discussion online.
I suggest to those who are interested in the subject a couple of links that may be helpful.
Driven to distraction – a research article by David L. Strayer and William Johnston – University of Utah (PDF)
Cellphone n.1 driver distraction – online article by Joe Benton – consumeraffairs.com news
Mobile phones and driving safety – a voice from Wikipedia
Le téléphone portable au volant – a study by the Observatoire national interministériel de sécurité routière (PDF)