Beginning last month, live video streaming of major league baseball games has been available via the popular $9.99 MLB.com At Bat 2009 app. Initially one or two games a day were available for free via streaming, with plans to roll out more and more games as the summer progressed. Baseball games are subject to local blackout, just as with broadcast TV. You can read more in a short article in the New York Times. It works on an iPhone or iPod touch, but you'll need to have iPhone 3.0 software, and likely also a 3G or WiFi connection.