A thermal camera is a great piece of kit that everyone should have in their tool box. The problem with them is that they are generally prohibitively expensive to own. Cheap ones come in at a couple hundred dollars but this solution leverages a cheap $80 off the shelf part and a Raspberry Pi Zero.
Although you might think that ordering a component and plugging it into the Rpi Zero's GPIO port it's really a hack, the MLX90640 thermal camera matrix isn't made for the Rpi and only comes with this beautify Windows based software.
Habr user Walker2000 had to communicate with the seller in order to get some documentation for the MLX90640. He then wrote a Python script that reads a frame from the camera 4 times a second and runs it through OpenCV. The script also adds some useful stuff like min and max temperature to the frames.
It's a great start to a niche that has been lacking.