Let's Make Robots!

Thermal

Heat Tracking Robot Arm/Head

Ok, I have been wondering if it would be possibly to build a robot head or arm that tracks thermal energy. You know how there are special thermal cameras that show areas of higher temperatures in different colors? I'm guessing those are pretty expensive, so would there be a simpler and cheaper way of building a thermal sensor? I was thinking of PIR sensors, but they can't really sense how hot something is, just if what its looking at is hotter than average.