Hmm, Do I sense an add-on board for Patricks Tuner?

I doubt you need one. Bear in mind that the tuner kit has 4 12-v compatible inputs, which can be read from the empeg end, as well as a pair of 12-v outputs. If the speed sensor is outputting a speed-proportional pulse train, it may be as simple as polling the correct input fast enough and converting the vaules to a speed.

pca