Don't try this at home....but seriously who has?
DISCLAIMER: yes, what I'm asking about and probably going to try is a horrible, dangerous idea and no one (myself included) should attempt to make such a device
but, has any other crazy person (Faith, perhaps? ;>) built a live steam injector for an oven that was not originally equiped with one? basically, all you need is a heat source, an enclosed vessel to hold the water, a nozzle that you can turn off and on in the baking chamber, and a safety valve to keep this device from exploding and scalding anyone nearby, right?