I have a candy thermometer, which I use but don't actually follow. When I first started making candy I didn't own a thermometer so when I finally got one I already knew how to tell the temperature. After using a thermometer I found out that they are much less reliable than other tests. I hear I'm supposed to calibrate it every time I use it, but that involves boiling some water every time I want to use it. So I put it in the pot and then promptly ignore everything it tells me.