Bonjour is a service discovery protocol. It is useed to find the other side, not to transfer data. For that, you'll need bsd sockets/CFSocket or NSStream or GameKit.
On the SQLite level, you'll probably have datestamps in each record. Time for creation and time of last modification if modifications are possible. Then you check the time of last sync and then send everything that's newer. Other side imports only things that do not exist or those with newer timestamps.