I mean it's kinda neat. A dishwasher is effectively just a big steamer, from a cooking point of view. I don't really see the advantage though. You'd be better off just using a crockpot, especially if you're cooking your food in sealed containers like mason jars.
On that note, that's probably an excellent way to cook meat. If it's cooked in a sealed container, it keeps all the flavor in. I'd be a little worried about a mason jar bursting open, though (doubt that'd happen in a dishwasher). I've heard tell that if you put a raw steak in a vacuum-sealed bag, and boil the bag, the steak turns out perfect.