I had a pet Savanah monitor lizard for 7 years. Crocket, that was his name. I wouldn't let him around kids much, he had a killer bite. Savanah's are supposed to be one of the most tame reptiles. Which is/and isn't saying that much. You couldn't teach him to use a litter box, nor could you call him out from behind the couch. He was entertaining, especially for a college-aged kid. I had to hand him over to a friend after I went into the Peace Corps. He died a year later. He was a good buddy, but I would never get another one. Big lizards like that belong in the desert, not in some f'g cage.
BTW: Check out those links MC posted.