For black and white I keep a couple nice thermometers on the shelves where I keep my chemistry. I go off ambient temperature and adjust the time. Mostly it's between 65-70°F. Lower level of my house, former utility room. I'm pretty lucky to have a nice spot.
Even with my famous Jobo processor I have doubts how accurate temperatures are controlled with color. Need a lot of thermal mass for stability.
I do usually control and check my temps with a photo thermometer, like everyone else. It's just that I could not help myself not to try this thing, seemed too obvious a choice .