There is a good news, Microsoft SQL Server 2012 Express LocalDB RC0 is Available Now.
LocalDB is a new version of SQL Server Express created specifically for developers. It is very easy to install and requires no management, yet it offers the same T-SQL language, programming surface and client-side providers as the regular SQL Server Express. By using LocalDB, developers don’t have to manage a full instance of SQL Server Express. This is a dedicated version of SQL Express for developers.
Microsoft introduced such a small and streamlined installer for LocalDB that the MSI has a size of 33MB only and it gets installed in less than a minute.
You can get the downloadable Installer MSI from; (Download from here)
LocalDB Utility: The SqlLocalDB utility (SqlLocalDB.exe) is a simple command line tool to create and manage an instance of Microsoft SQL Server 2012 Express Release Candidate 0 (RC 0) LocalDB. The tool is installed with the other SQL Server Express files in the Tools\Binn subfolder. To get more info on this visit: http://msdn.microsoft.com/en-us/library/hh212961(v=sql.110).aspx