Unfortunately, it doesn’t appear that those of us in the US can get it. Still, this link sheds more light on it, especially if you can read Japanese. And these brief videos offer a demonstration — it looks like an ebook, supplemented with pictures and videos.
The one app I could get from the US iTunes Store is ICHIRO51 Struck Out!, which is a game where you pitch to Ichiro and try to get him out (ideally, Struck Out!). It got boring pretty quickly.
Apparently the Mariners weren’t on board with this…
I looked at Topps Bunt for the iPad, but there’s no Ichiro card on there yet.
Oh, there’s also the iChiro app, which is good if you want to improve your posture.