A thermal imaging camera is an amazing tool and I would not conduct a home inspection without one! While thermal imaging does not allow an inspector to "see through" anything in a house; when used properly, thermal imaging can help a trained inspector to identify "clues" within a home that may indicate the need for a closer look. Over the past 5 years of inspecting I have found numerous defects that would otherwise be invisible to the naked eye, all due to thermal imaging.
To show you what I mean: These two photos were taken simultaneously by me, using a Flir E4 thermal imaging camera. The photo on the left side of the screen is the room as it looked to the naked eye. The photo on the right side of the screen is what the infrared camera "sees". The orangish/yellow spot on the bed was a cat taking a nap under the covers. I am normally not inspecting for napping cats, but this photo does a great job of illustrating just how useful a thermal imaging camera can be during an inspection!