Here's a story
at the New York Times
about Simplyaudiobooks.com and audiobook listening by commuters.
Audio book publishers have long known that listening to books is popular with commuters, but have never quite managed to crack this nut: how to breach all those locked garages and sophisticated car alarms to put samples of their goods inside vehicles.
I think the nut is getting cracked by the likes of Audible.com, Kitabe, and Simplyaudiobooks.com.