config_exporter.php

class ConfigExporter extends Mage_Shell_Abstract
{
    public function run()
    {
        $xml = new Varien_Simplexml_Element('<config />');
        foreach ($this->getConfigValues($this->getArg('path')) as $item) {
            try {
                $path = $this->_getConfigPath($item['scope'], $item['scope_id'], $item['path']);
                $xml->setNode($path, $item['value']);
            } catch (Exception $e) {
            }
        }
        echo $xml->asNiceXml();
    }

    protected function _getConfigPath($scope, $scopeId, $path)
    {
        switch ($scope) {
            case 'default':
                $path = $scope . '/' . $path;
                break;
            case 'stores':
                $store = Mage::app()->getStore($scopeId);
                $path = $scope . '/' . $store->getCode() . '/' . $path;
                break;
            case 'websites':
                $website = Mage::app()->getWebsite($scopeId);
                $path = $scope . '/' . $website->getCode() . '/' . $path;
                break;
        }
        return $path;
    }

    public function getConfigValues($path = '')
    {
        $collection = Mage::getResourceModel('core/config_data_collection');
        if (!empty($path)) {
            if (false === strpos($path, '%')) {
                $path .= '%';
            }
            $collection->addFieldToFilter('path', array('like' => $path));
        }
        return $collection;
    }

    public function usageHelp()
    {
        return <<<'USAGE'
Usage:  php -f config_exporter.php -- [options]

  -h            Short alias for help
  help          This help
  --path        Configuration path to export. This can contain wildcards using
                the '%' char, e.g. 'web/%'

USAGE;
    }
}

$shell = new ConfigExporter();
$shell->run();