it depends on a single term "high tempreature"
there are many out there, as coca cola said thermistors are good. I have also seen non-touch infared laser do the same. and yes there are kits already for them. I personally like jaycar in australia, as they have the kits, but typing in arduino temperature sensor into any search engine will get you tonnes of replies.
just try to figure out what range you need it for then you can narrow down your search alot