They were heating elements built into electronic enclosures that plugged into the auxiliary power outlets (called auxiliary power points in some vehicles) in automobiles, usually around where the gearshift is. The device itself was generally used to light cigarettes, but the port that it plugged into is also used for everything from phone chargers to GPS devices; it just supplies power.
I distinctly recall thinking that the glowing orange spiral that is the heating element was “pretty and glow-y” when I was about six, immediately before I stuck my thumb to it because the spiral pattern looked like my thumbprint. Clever child, I was.
In game terms they could be made from 1-or-more heating elements, electronic scraps, and maybe some scrap metal, and be parts that could install into a car, but aside from lighting cigarettes, just about the only thing you could do with them is cauterize wounds; they’re too small to cook or do chemistry.
