Not an intuitive item. I had a humidifier plugged into my bedroom. I noticed some discoloration on the outlet plug. I wasn't worried, but went ahead and flipped off the circuit breaker and popped off the cover. The outlet had melted inside, and the connector was glowing red hot inside. So, basically, we narrowly avoided a fire that would have started in my master bedroom, with us sleeping there. I've since used this to put every outlet in the house under load and checked for heat. I looked into thermal imagers, but those are expensive to even rent. This is accurate to record the temp of a grill top and many other surfaces you probably don't want to touch test.
It's a fun toy, and maybe a lifesaver. I'm not saying you need one, but if you have disposable cash around, think about it.