This sketch and suggested hardware ties together a cheap TM1638 based display and an off the shelf ultrasonic sensor to create a device that tells you how much further you need to go to be parked.
It's definitely a toy - something that would have traditionally been accomplished by "winging it" when parking, or using a string and a ping pong ball affixed to the ceiling. But when some of the electronic parts are so cheap these days, why not have a little bit of fun with it?
For more information, see my website for the full writeup:
See the supplied Fritzing file for the very simple schematics.
This project would not be possible without the following two Arduino libraries. Thanks to the authors who made their work available!