You're referring to experimentation with low-current, high-voltage pwm waveforms to cause neuromuscular contraction.
I've never experimented with it, but my understanding is that the waveform used by Tasers is proprietary.
I don't see the difficulty in creating such a system using a high-voltage AC inverter (available at the hardware store) and experiment with waveform modulation schemes using a current regulator, h-bridge or mosfet, and microprocessor.
Not much difference in theory between EMS and Tasers except for the waveform and amount of energy delivered. You should not need more than 20-40mA @ 50kV of power to experiment.