New iPhone Object APIs include login and synchronization enhancements.
See Developer Reference for iPhone > Reference > iPhone Client Object API > Synchronization APIs
See Developer Reference for iPhone > Reference > iPhone Client Object API > Connection APIs > Authentication
Message-based synchronization API enhancements include the beginSynchronize method, which sends a message to Unwired Server to synchronize data between the client and the server. The method supports synchronizing all data, or synchronizing only the MBOs in specified synchronization groups.
See Developer Reference for iPhone > Reference > iPhone Client Object API > Message-Based Synchronization APIs > Synchronize Data.