The message area you are referring to
is populated from Mage_Adminhtml_System_ConfigController::saveAction
.
Before the message is set, an event ("admin_system_config_changed_section_{$section}
) is fired.
code ref:
Mage::dispatchEvent("admin_system_config_changed_section_{$section}",
array('website' => $website, 'store' => $store)
);
$session->addSuccess(Mage::helper('adminhtml')->__('The configuration has been saved.'));
You just need to figure out what is in the section ($section = $this->getRequest()->getParam('section');
) and you would most likely be able to target an event specific to your section saving.
There is also an alternative solution: Use a Hint field in the admin section.
Place a HINT group into your system.xml configuration file.
An example:
<hint>
<frontend_model>dyncatprod/adminhtml_system_config_fieldset_hint</frontend_model>
<sort_order>0</sort_order>
<show_in_default>1</show_in_default>
<show_in_website>1</show_in_website>
<show_in_store>1</show_in_store>
</hint>
make sure it has the lowest sort order.
You will need to define the block class, below is an example, showing teh path as per the xml example.
It must contain a render method
/**
* Render fieldset html
*
* @param Varien_Data_Form_Element_Abstract $element
*
* @return string
*/
public function render(Varien_Data_Form_Element_Abstract $element)
{
return $this->toHtml();
}
You can then of course output whatever you need, and run whatever logic you need, via your block adminhtml_system_config_fieldset_hint
An example, to output some information about the installed extension: