When you need to startup WCF service conditionally - depending on your application configuration it is quite easy to achieve it by checking the ServiceHost.BaseAddresses collection. If your app.config file does not contain your service configured the collection will be empty. Here is the snippet:
ServiceHost host = new ServiceHost(typeof(MyService));
if (host.BaseAddresses.Count < 1)
return;
host.Open();
Next time I will post how to plug-in service startup in your application startup with a plug-in model i described in my post
Plugging-in application initialization code.