Super simple design but very handy and could potentially save you from damaging your car.

Use double sided tape to place this object onto your garage side wall, at driver eye hight. Position it so that the driver sees just a single line when the car is in the perfect parking position.

This will enable the driver to put the car in the same position every time with near millimetre accuracy.

This is a low-tech solution that doesn't need batteries, doesn't get in my way when using the garage for other things and works surprisingly well.

I printed my base in PLA and the beam in TPU but you can use whatever materials you have handy, just use contrasting colours.