How to open an URL with the default browser with FireMonkey cross-platform applications?

Regarding the answer of mjn, I have written the following unit. I have successfully tested it on Windows but I don’t have an OSX to test it on this platform. If someone can confirm it works, I’d appreciate.

unit fOpen;

interface

uses
{$IFDEF MSWINDOWS}
  Winapi.ShellAPI, Winapi.Windows;
{$ENDIF MSWINDOWS}
{$IFDEF POSIX}
  Posix.Stdlib;
{$ENDIF POSIX}

type
  TMisc = class
    class procedure Open(sCommand: string);
  end;

implementation

class procedure TMisc.Open(sCommand: string);
begin
{$IFDEF MSWINDOWS}
  ShellExecute(0, 'OPEN', PChar(sCommand), '', '', SW_SHOWNORMAL);
{$ENDIF MSWINDOWS}
{$IFDEF POSIX}
  _system(PAnsiChar('open ' + AnsiString(sCommand)));
{$ENDIF POSIX}
end;

end.

and I call it like this:

TMisc.Open('https://stackoverflow.com/questions/7443264/how-to-open-an-url-with-the-default-browser-with-firemonkey-cross-platform-applic');