Jump-start devices that plug into the cigarette lighter. Do they ever work? This editor has tried several that friends have purchased, and they've never come through. Many of these are promoted as with the same language as jump-start systems, focusing on the idea that you don't even have to pop the hood; but in reality (and explained by the instructions once you buy them) they're just trickle chargers and will do little for a conked-out battery in the cold. Save yous money, buy a high-quality set of heavy-gauge copper-wire jumper cables, and learn how to properly use them in an emergency.