One of my favorite Drupal-specific interceptions: if you are a president ...

special.php

/**
 * Implements hook_field_group_pre_render().
 */
function cwt_biography_field_group_pre_render(&$element, $group, &$form) {
  if ($node = menu_get_object('node')) {
    if ($node->type == 'biography' && $role = field_get_items('node', $node, 'field_biography_role')) {
      $role_term = taxonomy_term_load($role[0]['tid']);
      $is_president = !$role_term ? FALSE : _commissioner_uuid_is('president', $role_term->uuid);
      if ($is_president && $group->label == 'Responsibilities') {
        $group->label = t('Role');
        $group->format_settings['instance_settings']['attributes'] = 'id="role"';
      }
    }
  }
}