After hearing about Mass Effect for the iPhone, my first thought was, "Could they put Fallout on there, too?" Apparently Bethesda had the same idea at some point.
Speaking to Joystiq at E3, Todd Howard, the game director for Bethesda, said "We've looked into those things."
I think that the world of Fallout is unique enough that it could work on any platform. I think some of the things we do like VATS, I think that could translate to any platform, particularly the iPhone, We've looked into those things, we just haven't found the thing that supports the brand well. I wouldn't be surprised if it does happen one day. The iPhone versions that we've designed and said 'Ehh, we don't think we're going to do that right now,' there are ... there are a lot of them.
I suppose it's too much to hope we'll hear about one of them in the coming week, at Apple's developer conference.