Here's a great iPhone app from Major League Baseball - MLB.com At Bat 2009
From the MLB website:
MLB.com At Bat 2009
Exclusive pitch type, location, and speed data make At Bat 2009 the fastest, most detailed way to follow baseball on your iPhone and iPod touch.
Listen LIVE to every regular season and Postseason game including all home and select visiting team feeds and no blackout restrictions.
Watch the best plays of the game moments after they happen. The app will detect your connection speed to deliver the optimal quality video.
MLB.com At Bat 2009 costs $9.99 for the season.
Check out the full app description here in the iTunes Store
