One of the elements that no one has mentioned here, but figured into my opinion above, is that there is no direct action on the part of the person. This is what is known as grama, and automatically reduces the issue to one of m’derabonon. If we add to this the ambiguity of the prohibition of video, (what is the issur in video? The electronics don’t heat up if I walk in front of the camera, there is no fire, so what is the issur? electronic impulses? that is at worst a d’rabonon in itself), we have a case of grama d’rabonon where the person is not even aware of what he is doing, and does not want the end result. I cannot see how this would be assur.
In a case where the end result is a light turning on, the issue is one of hav’arah, creating a fire. But if the light is only a sensor, no heat, grama, don’t know about it, don’t want it (you do want it because of security? less justification for a heter), then I think it is permissible.
Somenone else here mentioned that soon many if not all public areas will be monitored by video. What then? Even now, I know of no one who stopped walking in the Old City because of this issue. The opinon that forbids walking in old Yerushalayim has been ignored and will be ignored in other places too.