here's one on the back of a mate's car (left hand side and the tow triangle) - basically you cut a length of old seat belt or harness material, loop it over, cut a hole and then bolt it to the car (e.g. to a bumper mount) with some big washers.
very light, doesn't protrude, can't hurt knees/pedestrians etc, cheap and easy to use
i wouldn't like to try and connect a tow line to the one in 89911's pic with a hot engine - it looks more like a trailer tie down
