i would use a stepper to control the RPM of a generator that does not have a governor. using android and voltage regulator to control the RPM and voltage.
What type of generator? Gasoline powered hone generator, 3 phase converter/generator, or something else?
Why a stepper motor? How would it control the generator?
Android? For remote control of the generator or as the processor for the control loop?
Voltage regulation to control voltage?
You have lots of holes in your description. If you do not plug them, your boat will sink!