Marty Lariviere [2] of the Kellogg School of Management [3] has written an entry [4] on his blog "The Operations Room" [5] about Uber [6], a company that has made it possible to hail car service from a smartphone.
Links:
[1] http://www.library.northwestern.edu/libraries-collections/evanston-campus/transportation-library
[2] http://www.kellogg.northwestern.edu/faculty/lariviere/research/
[3] http://kellogg.northwestern.edu/
[4] http://operationsroom.wordpress.com/2012/07/02/living-and-working-in-an-uberized-world/
[5] http://operationsroom.wordpress.com/
[6] https://www.uber.com/
[7] http://www.library.northwestern.edu/related-pages/transportation