I have no experience wit that item Richard, but I'm quite at home with electronic devices in general. Whether it is worth $40 is really up to you. If it does what you want and you can't build one yourself, and you really think it will add some visual interest to your layout then it is probably worth it for you.
The photos on Fifer website are rather small and the description does not mention any dimensions for the signal heads. So we don't know whether those are small enough for N scale. Too bad there isn't a close-up photo of those signal heads. I suspect that even if they are small enough, they will still not be very accurate representation of real traffic signal heads. You could contact Mike Fifer and ask him to provide you more info (and photos) of the signal heads). He is a member of the Railwire - maybe he will chime in.
