I may or may not have blogged here about this phenomenon before, as the first pilot programme was at the Safeco (Baseball) field here in Seattle. So it was a local phenomenon.
What they did was to allow fans with DS devices to download software that allowed them to get stats and player info, watch extra videos, order food and drinks and interact with each other during games. This "Nintendo Fan Network" will remain exclusive to Seattle through 2008, but Nintendo's winter marketing plan includes a slate of baseball, golf and monster-truck sponsorships and events that will put the DS to use.
This article in Advertising Age teases us about this program but doesn't tell us diddly about how this will be implemented, since the Fan network will remain exclusive to Safeco field.