The Nintendo Fan Network on the DS.

Maybe the AM radio will finally be replaced as the wireless device of choice for baseball fans. Nintendo is adding an ESPN partnership and other new features to enhance its Nintendo DS as a digital companion for people attending Seattle Mariners games, starting with Tuesday afternoon's home opener.

The Safeco Field experiment, now in its third year, uses a dedicated wireless network to deliver live game video, play-by-play audio, scores, chat, games, information and remote food-ordering to people in the stadium with the dual-screen Nintendo DS devices. The experiment is still confined to Mariners games -- Nintendo is the majority owner of the team -- but the company is hinting at the possibility of future expansion.

"This is still a trial, but obviously what we learn here and have learned here can be transferred to other experiences -- whether to additional stadiums within the sport, to other sports, or even beyond sports in general," said Zach Fountain of Nintendo's Gateway Group, which focuses on bringing the "Nintendo experience" to out-of-home venues.

The "Nintendo Fan Network" is free to DS owners at games, enabled via a software download to the device. To promote the expanded service this year, Nintendo will be offering free game-long rentals of the new "DSi" version of its device from Safeco Field kiosks for the first three months of the season. (Rentals have been $10 in the past.)

As a new addition this year, ESPN will be offering real-time sports headlines, stories and columns, plus an ESPN Zoom photohunt game on the devices. The addition of ESPN is another clue about Nintendo's plans for the network. The sports broadcasting giant probably wouldn't come on board for a single-stadium experiment without the prospect of future expansion.

Separately, Nintendo this year has added closed-captioning to the device. As of late last week, the final details of that feature still being nailed down, but Nintendo was aiming to let fans see the words of the radio broadcasters and public-address announcer on the screen. Fountain said it would be a popular way for people to get additional information and context without listening to a radio. (Update: The company said this morning that the closed-captioning system will only display the PA announcements.)

Of course, not everyone owns a Nintendo DS, but mobile phones are ubiquitous. So what about expanding the service to non-Nintendo mobile devices? Maybe a Windows Mobile, Blackberry or iPhone application? Nope, unfortunately, there's nothing like that on deck.

"Really what this application is all about is leveraging the dual screens, so it would be really hard to port to a different platform," Fountain said. "And we really believe the uniqueness of what we’re offering is really for a DS owner. With the huge number that are out there, part of the objective here is to create new ways for existing owners to experience their DS, beyond just playing games."

Coverage Note: TechFlash will be at the Mariners home opener to try the expanded Nintendo Fan Network and look for other tech angles at the game. Stay tuned for more Tuesday afternoon.