Gary over at http://www.builditsolar.com had been testing various solar air heaters with side by side comparisons and thermometers. He had also been keeping an eye on the slowly improving cost of infrared (IR) thermal cameras, since there are situations where looking at a thermal image can expose a simple and cheap missing-link in a design. He recently got ahold of a certain IR camera, with the cheapest model in this line of IR cameras being $1200...just to show why $150 + smart phone = a big improvement.
Pic is a dog (of course), but under his paws is a hidden in-floor loop from a radiant floor heating system. A gray mouse inside a gray bush is invisible to the human eye (especially at dusk/night); but to a snake, the mouse lights up very bright, especially on a cold night when there is more contrast with the cool background.