Having just entered the area of home automation, I think there should be applications where you can model your rooms, and then create your motion sensors, so that you can visualize the best placement of sensors. Almost like apps for garden sprinkler placement...infact, perhaps sprinkler apps might be used in a pinch for motion sensor placement 
Unlike video cams, setting up motion sensors seems to be working in the blind. If they have cool of times, then how do I even test what coverage am I getting.
