OBD stands for On Board Diagnosis. To make it short, it is a 10-15€ dongle that you can plug yourself on your car and which will enable your car to provide information to your smartphone through an app. This is more or less what we call "Valise" in french and I think is called "Car Diagnosis tool" and that you have to pay when going to your garage to check any issue.
I would like to know 2 things:
1° Did you know about this
2° Would you like to take benefit of that