It may be a while before I get around to this project as I have a few other projects with higher priority than this one. The main reason I latched onto the electromagnetic field sensing shown in the video is that I perceived it to have a lower failure rate than a PIR sensor. With PIR sensors one would have to be careful to position the sensor correctly such that there would be no way to pass through the doorway without the PIR sensor seeing the person. In addition, PIR sensors can be easily fooled by things such as a thick winter jacket which would absorb the IR pulse. On the other hand, with electromagnetic field sensing, as long as the sensing circuit is as tall as the door, there would be no feasible way to pass through the doorway without being seen (i.e. no need to be careful about locating the sensing circuit).
The bottom line was that, I perceived the electromagnetic field sensing to be much more fool proof than any cheaply available PIR sensor. Perhaps that is a rash judgement on my part, but in my experience PIR sensors are very easy to fool.