InAppSettingsKit is an open source solution to to easily add in-app settings to your iPhone apps. It uses a hybrid approach by maintaining the Settings.app pane. So the user has the choice where to change the settings.
http://www.inappsettingskit.com/
http://www.futuretap.com/blog/inappsettingskit/
A comparison chart and screenshots by author of InAppSettings:
http://inscopeapps.com/blog/inappsettings-vs-inappsettingskit/
