Wi-fi on public transit
According to Wi-Fi to Board the Trinity Railway Express in the Dallas Morning News, wi-fi will be installed on that area's commuter railroad. While it has been successfully tested on Caltrain in California, see "Caltrain Succeeds With High-Speed Internet," wi-fi hasn't yet been rolled out on the Caltrain system for regular service.
The trade publication Metro has a nice article too, "What to Consider Before Equipping Your Transit System with Wi-Fi." According to the article, most people in the field think wi-fi service is best suited for transit choice riders taking long trips, i.e., long rides from the suburbs to the center city.
OTOH, I think there are plenty of routes in the center city and inner suburbs that provide long rides appropriate for wi-fi and transit-choice riders. E.g., S buses on 16th Street NW, the new rapider bus service on Georgia Avenue, PikeRide and Rex in Arlington and Alexandria, etc.
And of course, the area's commuter railroads.