So I'm looking more and more into something like this and have been thinking about some of the parts and how I could adjust to my desire. First I don't really feel the need for a sight glass, they are nice, but extra money and cleaning. So that got me thinking about the temperature probe and I've been looking at a few others on the website.
There is this one
which is cheap and it says the probe and cable are water immersible and work up to 250*. If this is true could I just drop it in the center of the bag for an accurate reading? But for some reason this seems to easy/good/cheap to be true.
Otherwise, I was thinking about this one
which is a 1/2" and I figured I could attach it to a three way pipe joint coming out of the pump. That way I would get the temp of the fresh wort coming out of the pump and could also use it coming out of the plate chiller as well. It's more pricey plus I would need extra tubing, connects and a pipe joint.
Or I could just go your route minus the sight glass.