With regard to the case of the light in front of the house: while a sensor may be a switch, min hastam you have no idea which step will cause the light to go on/off. Therefore each step is a davar she-eino miskaven, which is mutar, because every davar she-eino miskaven that does not inevitably cause a melacha is mutar. This isn’t only my logic; I have heard this from many rabbanim.
I asked the Rav, and he said that if you don’t know exactly where the camera/sensor is, then it is ????? and therefore ???? ???????.