I came up with a Compoment and an Helper. I am sur there are better ways to do all this, do not hesitate to comments, even for saying how bad it is.

The component, store in controllers/components/view_in_file.php

Component Class:

<?php 
<?php
/*
 * ViewInfile component
 * will ouput the rendered view in a file as well
 *
 */
class ViewInFileComponent extends Object
{
     var $directory   = TMP;
     var $fileName    = '';
     var $Controller  = null;
     
       function startup(&$controller)
       {
             $this->Controller = & $controller;
     }
     
     /* set the file name for outpout, 
      * if clean is set to true the view rendered will be empty (only layout in html and empty div for ajax
      * redirect, if set (cake form ie : /Controllers/action/params), the output will contain javascript to redirect
      *           best usage is with "clean => true"
      */
          
     function setFile($filename, $clean = false, $redirect = null)
     {
        $this->FileName = $this->directory . $filename;
        $this->Controller->set('ViewInFile', array('file' => $this->FileName, 'clean' => $clean, 'redirect' => $redirect));
     }
     
     /* reset the file name for eventual next usage in action (not verified because hasRendered is set to true ..)
     */
     
     function reset()
     {
        $this->FileName = ''; 
     }
}
?>
?> The helper, store in views/helpers/view_in_file.php

Helper Class:

<?php 
<?php
/**
 * ViewInFile helper. Allow the rendered view to be captured to a file
 */
class ViewInFileHelper extends Helper 
{   
      /* we use afterRender to get the content of the rendered view and store it in the file (if found) */
     
    function afterRender()
    {
           $lview = ClassRegistry::getObject('view'); 

       $OutInFile = $lview->getVar('ViewInFile');
       
       if(!empty($OutInFile) && isset($OutInFile['file']))
       {
          if(isset($OutInFile['clean']) && $OutInFile['clean'] === true)
          {
             $out = ob_get_clean();
             ob_start();
          }   
          else
             $out = ob_get_contents();
          
          /* this might not work in PHP4 ?? */
                     
          file_put_contents($OutInFile['file'], $out);     

          if(isset($OutInFile['redirect']) && !empty($OutInFile['redirect']))          
          {                         
             echo '<script type="text/javascript">';
             echo 'window.location.href="'.FULL_BASE_URL.$lview->loaded['html']->url($OutInFile['redirect']).'";';               
             echo '</script>';
          }
           }   
    }
    
    /* Allow to get the file name into the view itself */
    
    function getOutFileName()
    {
         $lview = ClassRegistry::getObject('view'); 
       $OutInFile = $lview->getVar('ViewInFile');
       
       return is_array($OutInFile) && isset($OutInFile['file']) ? $OutInFile['file'] : null;          
    }
}
?>
?>
Usage in a sample Contracts controller that has a test() action and of course a view.

The view

/Contracts/test.ctp
<h2>ViewInFile Test</h2>
<p>This content in file : <?php echo $viewInFile->getOutFileName();?></p>


Controller contract

[p]The function test() is setting the file name, set the clean flag to true (the existing output will be cleaned) and a redirection after rendering. Note that after calling $this->render(), you can get the produced file and do whatever you want of it. For my test, I just show it into the cake error.log file.


<?php
class ContractsController extends AppController {

    var $name       = 'Contracts';
    var $helpers    = array('Html', 'Form', 'ViewInFile' );
  var $components = array('ViewInFile');

  function test()
  {
      $this->ViewInFile->setFile('mytestfile.html', true, '/Customers/index');
      $this->render();
    $a = file_get_contents($this->ViewInFile->FileName);
    LogError("file content : ".$a);
  }
}
?>
Another usage, this will render the view and capture it previously.

  function test()
  {
      $this->ViewInFile->setFile('mysecond.html');
  }

Important: the file does not contain the layout, but the view does (if $clean !== true).
I have tested, mainly for my needs using cake 1.2.0.5427alpha (from the branch). The redirection works also when it's an ajax request.