It should have been there when it was first introduced: FaceTime videoconferencing between iPhone/iPod touch and desktop computers. The latest rumor is that it is coming. For Macs, Apple could incorporate FaceTime support in iChat. The article doesn't mention how they are planning to do it on Windows.
This rumor, however, comes from the French site that claimed iLife'11 was coming on August 7, with a new mystery application. Neither the mystery application nor the iLife'11 suite materialized at that date.