In a rather surprising (to me anyway) move, Vir2L, a sister company of Bethesda's, today announced a version of Oblivion for mobile phones. They put up a press release along with screenshots from the actual game. It's release is scheduled for mid-April, 2006.

Press release Elder Scrolls: Oblivion for mobile phones
Oblivion for mobile phones screenshots
Oblivion for mobile phones trailer