I have an S and a 3, using the fob is way better than the phone app. The fob uses a direct low latency connection, when using the phone app I often have trouble connecting or get disconnected in the middle of a session and the latency is noticeably higher. You want low latency control so you can stop it in time if it's going to hit something.
I'm really hoping the Model 3 fob comes out soon and is available to all 3 owners.