You can implement your action in a separate file in your setting bundle. it'd better use preference_bundle template provided by theos. About URL, you can have a look at this, https://github.com/hbang/NotiQuiet/blob/master/prefs/ADNQListController.m I have test the method openURL, it still works although this file was written 8 months ago.
For details, http://iphonedevwiki.net/index.php/Preferences_specifier_plist this is always helpful.