Options for keeping two SQL Server Compact databases in sync?
From the development perspective, you could try the Microsoft Sync Framework.

For further information about Microsoft Sync Framework, refer to the following links:


http://msdn.microsoft.com/en-us/library/bb726015(v=sql.105).aspx
https://stackoverflow.com/questions/581110/using-ms-sync-framework-to-synchronize-two-sql-ce-dbs