Hand held gas analysers

Are those sub $100 hand held carbon monoxide analysers worthwhile if one wants to look at the efficiency of your stove? Or is it better to look at carbon dioxide if one has to keep inside a budget?

Eg. https://www.amazon.com/Handheld-Monoxide-Precision-Detector-0-1000ppm/dp/B0174Q3RVG

That doesn't look like it's designed to sample hot flue gases. It's an ambient CO detector which would be worthwhile if you were heating an indoor space with a RMH and you wanted to assure yourself that it wasn't leaking or backdrafting.

Peter van den Berg would be the definitive authority on what sort of analyser is worth getting.

Yes, it doesn't have a probe as such.  But I was wondering if I could hold it above the flue for a short period.  At present my flue is about 30 deg C at the top.