C Builder XE2 introduce the new dbExpress ODBC driver, which enable FireMonkey and VCL applications to connect to any database that provides a ODBC driver.
In order to show how it works, I created a FireMonkey project sample that connect to a PostgreSQL database.
As first step, you must install the PostgreSQL ODBC driver on the machine that will run the application. Second, applications compiled as 32-bit, requires the

For 32-bit applications use c:\Windows\SysWOW64\odbcad32.exe

For 64-bit applications use o c:\Windows\system32\odbcad32.exe

Instructions for windows 32-bit

• Use c:\Windows\system32\odbcad32.exe

The next step is to create an dbExpress ODBC alias on Data Explorer, where the Database Name parameter is the name of the Data Source created earlier, in my example the Data Source is called PostgreSQL35W. The database, username and password was already defined in the Data Source, but you can override the username and password parameters through the SQLConnection.

Assuming you already know how to use the SQLConnection, DataSetProvider and ClientDataSet or SimpleDataSet ,and DataSource components, just connect all the components as you usually do. The SQLConnection will look like this:

  object SQLConnection1: TSQLConnection
    ConnectionName = 'PostgreSQLOdbc'
    DriverName = 'ODBC'
    LoginPrompt = False
    Params.Strings = (
      'drivername=ODBC'
      'Database=PostgreSQL35W')
  end

You can use the dbExpress framework when connected to a database through dbExpress ODBC driver. In XE2 the ODBC driver is compatible with Windows, we are evaluating the possibility to support this driver on Mac.
The figure below shows the FireMonkey application connected to PostgreSQL via dbExpress ODBC driver. Now you can connect to any other other database not supported natively by dbExpress.

Download the source code here.