One of the fears of winter driving is getting in your car at 7:00 in the morning, turning the ignition and all you hear is "Errrrr...errrrr...click...click...click" then nothing. Maybe it was the wind or a stray dog that unplugged your cord or it could even be a bad cord or heater, either way you're calling a cab to get to work. There are quite a few manufacturers that include a little status light in the female end of an extension cord but as far as I'm concerned this is next to useless because it is just an indication of available power not a test of the actual load. What I wanted was some way to sense the current draw, kind of like a clamp-on ammeter.
After a bit of internet window shopping, I came across a device that did almost everything I wanted. For about $20 you get a little adapter that you either plug in between your cord and outlet or cord and block heater and an LED indicates current. Perfect...except that I sure don't want to venture out in the deep freeze, to check that little light, any more than I have to.
This then is my project: A current monitor that can be embedded in an outlet box inside your home so you can monitor the use of a block heater or roof heating cables etc.