The iPhone revolutionized the way in which phones are used. With more screen "real estate" for video and graphics, it opened the door to delivering a wide variety of learning opportunities to individuals on the go.
With gigabytes of storage, connectivity, and a larger screen than any phone/PDA before, we now have a canvas on which to paint the mobile learning environment of the near future.
It is the perfect medium for enhanced podcasts and vodcasts - the kinds of things that populate iTunes U! http://itunesu.pbwiki.com/