We have an INotificationProvider which does this.
var settings = orchardServices.WorkContext.CurrentSite.As<CustomSettingsPart>();
yield return new NotifyEntry
Message = T("Property needs setting"),
Type = NotifyType.Error
The problem is, when updating the CustomSettingsPart through admin, because of the ordering (I'm assuming) if I update another *SettingsPart it'll never update because it'll fail the INotificationProvider check.