Thermovision is only the latest step in humanity's quest to "see inside stuff" (not actually quoting anyone here; just trying to make the topic sentence seem more authoritative). The first and most popular method, the window, is still in use today, although one's most attractive neighbors all too often employ countermeasures like the curtain, the Venetian blind, or the phone call to the police.
Centuries after the introduction of the window, Wilhelm Conrad Roentgen's X-rays stunned the world—not an actual X-ray of Roentgen's lungs or anything, but his announcement that X-rays could produce a photographic image of people's innards. Scientists around the world set out to duplicate his experiments. In 1896, Professor Frank Almy of Grinnell College produced "cathodic ray photographs" of frogs, keys, and coins, although some colleagues dismissed his experiments with keys and coins as "horsing around." Still, it must have been pretty tricky to get the frog to swallow the keys and coins, not part of their regular diet. (Maybe he told the frog that the keys and coins were delicious flies. Frogs like flies.)
The medical community immediately grasped the potential of this new technology, but it was only when the Coolidge tube replaced the unreliable Crookes tube in 1913, and nitro-cellulose-based photographic film supplanted glass-plate negatives in 1920 that radiology become a meaningful addition to the doctor's bag. Not that you could actually fit a whole X-ray machine in a doctor's bag. Unless it was some kind of giant bag. Then how could he carry it? He'd probably injure his back. Which could be clearly shown on an X-ray. Which he couldn't carry. My head hurts.
In the 1920s fluoroscopes were found in many shoe stores (not found in the sense of somebody lost one and then it turned up, but more in the sense of—there they are, fluoroscopes, right here in this shoe store!) allowing customers to see the bones in their feet that would soon be scarred by hideous radiation burns. This danger would not be fully apparent until the 1950s, and by then the guy who thought up this dangerous and irresponsible marketing ploy was long gone, as fast as his horribly deformed feet could carry him.
Recent years have brought exciting advances in imaging techniques (as well as some attractive new styles of shoes). Computed Axial Tomography (CAT scan) produces a cross-sectional image of the harder structures of the whole body. Magnetic Resonance Imaging (MRI) does away with X-rays altogether, instead employing a superconducting magnet to generate images of inaccessible soft tissues. And Positron Emission Tomography (PET scan) enables us to see some other things in a whole other way. Or something like that. But whether or not this constitutes a crime will be up to the Supreme Court to decide, a decision they'll have to make while wearing robes that science has made all too transparent. Even Justice Rehnquist's. Ewwww.
You can see some cool medical images here.
Heat Sensitive Answer
Some Oregon cops with no warrant used the Agema Thermovision 210 to see through the walls of Danny Lee Kyllo's house to learn if he was growing marijuana.
This thermal-sensing device can detect the heat the cops figured came from high-intensity lights that can be used for indoor cultivation. Once they saw the hot spots, they got a warrant for a conventional search. They picked the Kyllo place because Danny Lee and his wife had previously been busted on drug charges.
Kyllo argues that the warrantless scan by the AT210 violated Fourth Amendment protections against illegal search and seizure, and San Francisco's 9th Circuit Court agreed, but later reversed itself when one of its members resigned. The question here: Does this scanning constitute a search?