Build an ultrasound car parking aid
Parking spaces in buildings are as small as possible to avoid wasting precious real estate. Furthermore, such parking spaces are often surrounded by concrete pillars or delimited by walls, making it difficult to move a car into such a tiny reserved space without scratching its precious metallic paint. Add to this that cars only get bigger and you will understand the need for an electronic parking aid. Here is a simple solution based on cheap ultrasonic transceiver modules.