I asked questions about this, and got some sugestions from people. I started with the assumption I wanted to have extra fields on the homepage that would appear in the footer on every page. In the end I created a special footer page, but the basics are the same.
http://silverstripe.org/themes-2/show/271952#post271952
Must admit my starting point was all wrong - do not try to get the absolute parent, it does not work and it is apparantly too resource intensive. But there is a sugestions at the end on how to make a page undeletable and unique.
I ended with adding this to the controler of my page.php to make the function accessible to all pages that use it as a base class.
//showing footer info
public function Footer(){
$myFooter = DataObject::get_one('FooterOfPage');
return $myFooter;
}
I then used a footer.ss that I inluded in my page.ss with the code:
<% control Footer %>
$ContentforFooter
<% end_control %>
And added a nice icon (a nice 'F') to the footer page in the backend with:
static $icon = "themes/annomedia/images/icons/footer";