...other than displaying the approx. temp of the fourth cylinder's exhaust (ideally from what I read) and indicating whether or not one may detonate when hitting around 1650+ degrees... what else can it help determine about the car's health?

Lets you know if you are running lean or not. 1650 is a little high IMO to be tuning around....1600 would be the absolute max I would tune to. It was also one of my indicators that showed I had a problem with my motor when I lost compression in a cylinder....I was reading about 50 to 100*C higher than normal.