I think this is a tool that would come in handy. The obvious application is detecting air leaks to increase your home’s R-value. Maybe that application alone makes it worth it.
But coming back to the “seeing through walls” thing, you can get creative. E.g.: Have a clogged pipe? Run hot water down the drain and see where the image stops showing heat in the pipe.
The high rated FLIR C2 Compact Thermal Imaging Camera is $500, which is out of my budget.
I’m looking at buying something like the Seek Thermal Compact Imager, which is around $200. It plugs directly into your smartphone and is more aimed at the consumer level. However, I do not know if this camera is good enough to see through walls, like the FLIR can.