I have found the answer, incase anyone else needs it, it is:
$this->getSkin()->getUser()->isLoggedIn()
and with this function you can check if the user is admin:
/**
* Returns true if user is admin.
*/
protected function userIsAdmin() {
$isAdmin = FALSE;
if ($this->getSkin()->getUser()->isLoggedIn() === TRUE) {
foreach ($this->getSkin()->getUser()->getGroups() as $key => $group) {
if ($group == 'sysop') {
$isAdmin = TRUE;
break;
}
}
}
return $isAdmin;
}