I'm building a semi-automatic shifter for a formula car. I'll post the full design for it once the car is in the competition. I just want to leave it semi-proprietary until it's not relevant for this season. We have an ECU that puts out a square wave signal.
edit, I forgot to actually say what I was using the value for!
I'm making a semi-automatic system, so you can queue shifts and it will wait for the RPM to be at the optimum value to shift, reducing loss of power and making shifts on curves easier.