Recently, infrared cameras have become available as smartphone accessories. Being less expensive than regular infrared cameras they are readily affordable for schools and many teachers may even privately own one due to their potential to visualize all kinds of thermal phenomena in physics teaching. Any science teacher who wants to use such a camera must know some characteristics of the camera when trying to properly understand the observed phenomena. We compare models which are presently available, discuss which facts any user should know, in particular the spatial resolution, and present a number of qualitative experiments for physics teaching with such a camera.