Formula 1 race cars have a piece of wood (albeit a slightly specialized type of wood) secured to the bottom of the car. At speed, the ground effect of the vehicle loads the suspension and lowers the ride height of the car. There are rules as to the minimum ground clearance allowed, so the piece of wood is set such that it wears if it hits the ground. By measuring the thickness of the piece of wood after a race, it can be determined if the car was too low at any time. Low tech solution to a high tech problem.