Sync Services provides a powerful and extensible mechanism that enables
data to move seamlessly between multiple Macs, devices such as mobiles
phones and PDAs, and network services. This ability has long been a part
of Mac OS X , through iSync and .Mac, which could manage contacts,
calendar items, and bookmarks. Now in Mac OS X v10.4 Tiger, any Mac OS X application
can tap into this functionality to sync any kind of data reliably,
frequently, and easily.