The factory transmission controller uses a signal from the TPS but I don't think that would be necessary for a stand-alone controller, all the transmission needs is a governor pressure signal and commands to lockup the converter and engage the OD. The RH conversions that use pressure switches on the governor pressure test port function by road speed and I think a stand-alone controller could too.

The major challenge, as I see it, is to determine what voltage equates to what governor pressure and how many pulses from the output shaft speed sensor equate to what road speed.

If this can be pulled off it will make a lot of previously unusable RE's usable for retrofits....hope it happens.