I think Scott is confusing the issue by convolving the Sling streaming function with the Hopper Transfer app. I don't believe there is any such thing as a "Sling Transfer" program. But I sure wish there were!
For straightforward streaming from the Hopper w/Sling to your PC or mobile device, various handshakes and validation occurs between the Hopper, Dish servers, and the sling client whatever it is. Eventually the connection is made and the audio/video sling data stream starts up. The data stream goes direct from Hopper to a local device over your local LAN. If you are somewhere other than where the Hopper is, then that's where the stream goes; over the Internet. It does not go up to Dish servers and back down to where you are.
If the Hopper or local device are only connected via wifi, then that's how it goes. I would not call wifi a "key". In fact, if you can avoid wifi, it's better because you don't want anything (such as a microwave oven) delaying or dropping those packets.
Now as far as the Hopper Transfer app is concerned, that requires your cooperation on the Hopper to transcode the program for iPad playback. I believe that may have to go over wifi if the iPad is connected via wifi. But I have neither a Hopper w/Sling nor an iPad, so I can't say for sure how this works. But the end result is the transcoded program sits on your iPad and you can take it and view it later, via the iPad, anywhere, even disconnected from any network.
