BuddyPress.org

Look at MobilePress and WPTouch for ways to show different looks of a WP site to mobile users (the latter is especially for the iPhone). There are at least a few other stylesheets and templates as well. I have an iPhone, and these have been decently successful on standard WP sites. The iPhone browser uses MobileSafari.

What I would really like to see is an iPhone app that would allow you to browse almost ANY Buddypress site with a standard look-and-feel.