I borrowed a hall effect pedal as used by the Zilla. In theory it should have worked with the Simovert, but in practice, it doesn't. The hall effect pedal requires a fair amount of current to operate and the Simovert only supplies 24mA into a short circuit. When the pedal is connected it's throttle pot voltage drops from 5v to 3.2v which isn't enough to make the pedal work.
I did try adding an external power supply and while it did work I saw some oscillations in the input reported by the Simovert. Even if there were no oscillations, I'm not happy with this from a reliability point of view so it's back to the drawing board. I can use the original throttle pedal and make a box to hold the sensor supplied by Metric Mind or I can try the VW drive by wire pedal which provides the resistive divider the Simotion expects.
Click for more details including a pinout with functional descriptions for the Zilla pedal.