If you're using a 6D then why not just use the WiFi remote on your cell phone to compose and focus the shot?
That could work great for a farther away shot, or environmental portrait. For a closeup though, it could be hard to use the phone to focus on your eyes if they are looking down at the phone rather than at the camera lens. It could certainly help you line yourself up in the frame, and set the focus point approximately, but there will still be some trial and error if you're using a typical fast portrait lens. Controlling the 6D is also kind of PITA from an iPhone, to be honest. I set it up once and tried it, but I've yet to actually have a practical use for this function. I could see it being useful for stealthy wildlife work, where you plant a camera and sit a ways away in a blind with your ipad