There is or was?? A system called the GEM 2000 that tells you a lot more then on and off. It is an LED light that comes on with your power. It can tell you all kinds of things depending on how it blinks or stays on but it would be just the thing for you. About 30 bucks though so it's not all that cheap. I have a couple on planes and like them. I also have the volt watch. My problem is I tend to forget to look at the things most the time and have to bring out the instructions to figure out what the GEM is telling me. The volt watch is the simple way to do things, just have to mount it someplace you can always see it, I tend to hide mine then forget it's there. They call these my Golden Years!!!