Showing a pop-up message from Business Rule?

You've mentioned a couple of different requirements but the most basic "Message Here. Click OK" dialog box can be quite easily achieved. There is some sample code in there already when you create a new dashboard extender rule. The code looks like the below. I chopped and mashed some stuff together from something already written but you should get the picture:

	Public Function Main(ByVal si As SessionInfo, ByVal globals As BRGlobals, ByVal api As Object, ByVal args As DashboardExtenderArgs) As Object
			Try	
				Select Case args.FunctionType
					
					Case Is = DashboardExtenderFunctionType.LoadDashboard					
						If args.FunctionName.XFEqualsIgnoreCase("setComponentValues") Then												
							If args.LoadDashboardTaskInfo.Reason = LoadDashboardReasonType.Initialize And args.LoadDashboardTaskInfo.Action = LoadDashboardActionType.BeforeFirstGetParameters Then
								Return nothing
							End If
						End If
					
					Case Is = DashboardExtenderFunctionType.ComponentSelectionChanged
						Select Case args.FunctionName
							Case "something"
								Dim selectionChangedTaskResult As New XFSelectionChangedTaskResult()
								selectionChangedTaskResult.IsOK = True
								selectionChangedTaskResult.ShowMessageBox = True
								selectionChangedTaskResult.Message = "Hello World. Click OK to continue."
								Return selectionChangedTaskResult
							Case "somethingElse"
								Return nothing
						End Select
					End Select

				Return Nothing
			Catch ex As Exception
				Throw ErrorHandler.LogWrite(si, New XFException(si, ex))
			End Try
		End Function