You have just returned from the grocery store. Of course, you would rather not make ten trips from the car to the door and back. So you gather up as many shopping bags as you can possibly carry. And then there you are, standing in the dark. You try and tap the light switch, but by the time you found it, half of your groceries have already crashed to the ground. Or you stub your toe, because you can't even see where you are going. Motion detectors fix this problem, once and for all. And, what's more, the lamps in the house never stay on unnecessarily. Practical and economical.