I recently had a project where I needed such a sensor, and I picked up a TF-MiniS, which is a popular IR distance sensor. They aren’t very expensive, and they work serial or I2C. So how did it do?

Researchers have finally figured out how mosquitoes see humans in the dark: They detect infrared light the body generates via heat.

So how do those cameras work? By definition, a thermal camera is a non-contact device that detects infrared energy (heat in this case) and converts it into a visual image.