Business (oh sorry, 'start up') idea: Some kind of lidar based system that can guide you to an empty space in a large and busy car park.
Inspired by spending 15 minutes looping around the long stay car part at Heathrow, and not being dissuaded by the people who just parked along the access roads.
The inverse problem has been solved in a couple of ways: Taking a photo of the provided section and row letter/number combo, and leaving an AirTag in the car.