I don't think the sender is part of the intent so it is not available to get. You might send some piece of data with it when you start it I guess, that way, you would know it was from your app. Others would not send it and you would know it was from some other app. Something like that.
Of course any app that knows what to do with your service could send it information about itself. Otherwise, if your app is just registered to handle certain things and apps just broadcast for the app that best handles their content, well you can see the problem. They wouldn't know whether your app was going to handle it or not. But all of your activities that require that service could.
Hope this helps.