http://drupal.org/node/64580

gmap_location.module

@@ -136,7 +136,17 @@ function gmap_location_node_page($nn=null) {
           $newmarker['label'] .= image_display($n,'thumbnail');
           break;
         default:
-          $newmarker['label'] = strtr(theme('node',$n,true),"'\n\r",'"  ');    //make sure it all goes on one line.
+          // Allow a module (where the module name matches the node type name)
+          // to define a custom display for the google map label.
+          // For this to work with flexinode defined data types,
+          // a module called 'flexinode_#.module' in your site's module
+          // directory and add hook_gmapnodelabel($node, $location) to it.
+          // Be sure to enable your 'flexinode_#.module'.
+          if($labelresult=module_invoke(strtr($n->type,'-','_'), 'gmapnodelabel', $n, $locn)) {
+              $newmarker['label'] = strtr($labelresult, "'\n\r", '"  ');
+          } else {
+              $newmarker['label'] = strtr(theme('node',$n,true),"'\n\r",'"  ');    //make sure it all goes on one line.
+          }
       }
       $newmarker['point']= $locn->latitude.','.$locn->longitude;
       $newmarker['markername']=variable_get('gmap_node_map_marker_'.$n->type, '');