I think most of you are assuming that RJ has a Mac somewhere in their office. The iphone dev kit only runs on a Mac. If RJ is a Linux shop or a Linux shop with Windows workstations, then they're gonna have to go out and buy a Mac. Plus, it's $99 a year to be in the program.
I'm not sure sure there's enough interested members to get a good return on investment. And add to the fact that apps are pirated almost as soon as they're introduced. Even the crappiest 99 cent apps get ripped off these days.
And as others have said, the iphone isn't the only phone out there. The RJ tech team just needs to make the site more mobile friendly, in general. Or at least the parts that pertain to workout plans.