Is there a demand for this?

Just doing a little market research to gauge if there's any interest in my idea. What if there was a sensor that you could place place over your light wiring that could close/open a relay when the light was turned on or off. This sensor would not require any cutting or damage to the factory wiring, avoiding any warranty problems or hacked up wiring. For example you could turn on/off a light bar when the fog lights were turned on/off.

What got me thinking was this christmas I put a wreath on the back of my truck that lit up when the brakes were pressed. To operate the 120 volt relay I put a vampire tap on my brake light wiring, all the while thinking there's got to be a better way. A few minutes with the google didn't provide any ready made products, but a trip to the geek side of the net showed some potential integrated circuits that a nerd like me might be able to use. I don't know if I can make it or not, but a potential market might make it worth looking into.

 

Ingenious, but pointless.

 

anybody else?