The door popper just unlocks/unlatches the rear door so that when you get back there, all you need to do is pull it open. An automatic door hasn't been done (yet) since it'd be rather involved to add the electric motor or hydraulic drive mechanisms to actually open the door for you.

It's a cool idea though and you should take plenty of pictures and write up a How2 when you make this conversion ... so we can all copy you.

I've had the idea knocking around in my head for a couple of years to convert my rear door to a lift gate. I just haven't been able to prioritize it enough yet to get started. I even have an extra door on hand (with a bad hinge) to do the project.