Picked up some Uberwaycoolawesomeradirificwunderbar tid bits - the 100 psi relief valve and a solenoid valve to control the boiler inlet water. The way this will work is, the water pump will run all the time at 100+ psi and the solenoid valve between the pump and the boiler will be open until the water level sensor (on a 2 second delay) tells it to close (when the boiler coil is half full). I needed a high pressure pump because when the solenoid valve is open, the steam pressure in the system will try to push the water back to the pump and the inlet water has to be able to overcome this.
I ordered a steam pressure/temperature gauge today. When my paycheck comes I'll order the $$ deep fryer thermostat. That will take care of the major components except for the battery.