Seek Thermal Camera for iPhone, using a lightning connector. I am using this on an iPhone 6.
It has the ability to sense temperature differences within 1 degree and can display the temp on screen of the object your looking at.
It has an option to display both highest and lowest temps in the frame and a mode to highlight only items that are above the temp threshold you set. It offers several color pallets to choose from, I fin outdoor shots are better in white or black scale and indoor shots of cold spots are better in the "Iron" setting.
Panning quick distorts the video but it does well once you slow down.
I bought this to look at the cold spots in my house so I can add insulation. I'm having fun with it in other ways as well, but it is doing the job I intended. Amazing to find out how many light fixtures were never insulated after they were installed.