Once installed, it'll give a warning sound if the headlights are left on while the engine is off. The package says it requires no tools to install, and that it's for cars, trucks, and boats.
I don't really know when this was made, or anything about automobiles, so I don't know if it's compatible with modern vehicles. I believe that if you have a "fuse block" in your car (under your dashboard), then you can install it.