Using Arduino to read RPM in car

So I'm looking to use an arduino to read RPMs in my car, I'd like to use the OBD part, is this possible I can't seem to find much on it, or any other suggestions.

Thanks!

OBDuino

They are using the ELM-327 interface to extract the OBD2 information.

I am interested in the project.
Can we implement the ELM327 function on the Arduino?