I have a wood stove in the basement that is connected to the chimney flue with stovepipes. It has adjustable air inflow like most wood stoves, but it has always been a guessing game where I should set the intake ports. Too hot and you risk a chimney fire, too cold and you get creosote buildup in the flue.
I purchased the Magnetic Stovepipe Thermometer on a whim a few months ago. I thought it might be interesting to know how hot the stovepipe got. As it turns out it’s a great guide for how to set the air inputs on your stove. Now, every time I walk downstairs to check the fire, the first thing I look at is the stovepipe thermometer. If it’s pointing near to straight up I know the temperature is about right. If it’s pointing left I know it’s too cold, so I open up the air ports and/or add more wood. If it’s pointing right I know it’s too hot, so I close down the air intake ports.
I don’t believe the model I purchased is any better than the half a dozen or so I found on Amazon. Others could very well be superior. The fact that it is magnetic, however, is very convenient, as you can move it around on the stovepipe till you find the hottest spot or the right angle.