I've never understood the thermometer in the kettle. It gets in the way of an immersion chiller, it will tear your bag in BIAB, and since it's getting bumped a lot from a chiller or stirring, it is usually inaccurate. It is also only a one-trick pony.
I always s suggest that you buy a thermapen. It can be used to measure strike water, mash temps, sparge temps, and kettle temps. Not to mention it's use on the grill or in the oven. Often they are on sale, too!