I saw something in Autozone yesterday that made me laugh. It was solar-powered scanning LEDs, you just stick it on your dashboard.
Anyway, that thing looks similar to the solar-powered fake I saw, similar enough that any theif might think you're faking an alarm and will go for it. Whether or not your alarm does go off and they run off, you will still have a broken window or two to deal with.
If you are adament about the idea of a scanner, I would rig up several red LEDs and drill them in through the Contour plate on the dashboard, bout 1 inch spaces between. It would take a lot more time and ingenuity than just plugging that thing in, but would look pretty awesome IMO...