Custom enrichers

Now that I think I have my fuel rate PID working, I’d like to figure out how to calculate (very rough) fuel consumption. This is a function of the fuel rate (mm3 injected into each cylinder), RPM and speed. If I’ve understood things correctly, an enricher might be able to make the calculation, but how can one add a custom enricher?

I have looked at the roll_pitch_enricher, and I think I understand how it works and could use a similar approach with a fuel consumption enricher (that would work with the OBD manager), but how and where does one add a custom enricher? Custom code sounds like a logical place, but the types available there are only Execution, Utility, Returner and Service.