I just purchased one of these at napa yesterday. The guy that worked there helped me out quite a bit since he was in the repo business also lol 
anyway its pretty simple just run this in line with your battery. Im putting this in my cab under the seat. That seems like the best spot for it; and if someone were to see it they probably won't know/care what it is. All you would see is the little stem sticking out of the carpet.
Those do work good since without the key they become somewhat invisible, as to the repo guy he's yanking your chain. He will have your car no matter what you do to it, I don't need no stinking key to take your ride, people try that all the time with me here and I can almost load it just as fast with or without the key. Even when they park it between two cars, some of the officers are amazed at how such a big truck that I drive can squeeze a car out of a tight spot when the truck won't even fit.
