Yes. It has existed for quite some time under various names using various sensors. Some common names are thermal imaging and forward-looking infra-red (FLIR). The technology is based on detecting and measuring infrared radiation near 15 μm wavelength. This happens to correspond to the peak of the blackbody emission spectrum for objects near 300K, which is approximately room temperature.
There is an atmospheric transmission "window" in the 8 to 12 μm as well as the 3 to 5 μm infrared band that makes thermal imaging detectors practical. In the 1970s we used detectors cooled with liquid nitrogen, HgCdTe (mercury-cadmium-telluride) detectors to detect infrared radiation in the 8 to 12 μm band and indium antimonide (InSb) detectors for 3 to 5 μm.
Sometime in the mid 1970s, I experimented with un-cooled pyroelectric broadband infrared detectors, manufactured here in Ohio by Harshaw Chemical. Pyroelectric detectors were experimental at the time, and difficult to use because they depended on a temperature gradient to move a fixed charge around to produce a signal. Staring a fixed scene produced no output at all, no matter what its temperature. So, I placed a mechanical chopper wheel in front of one so it alternately "looked" at the back of the chopper wheel or (in between the blades) out into the room. An op-amp with an FET front-end converted the charge movement into a small current, which appeared as a small voltage at the op-amp output, a configuration commonly called a transimpedance converter or amplifier. Even so, I had to use a PAR (Princeton Applied Research) lock-in amplifier, synchronized to the chopper wheel interruption rate (about 100 Hz), and a long integration time on the order of ten or fifteen seconds to see any detectable change in the pyroelectric output when I allowed the detector to "see" my relatively hot body against the room-temperature background radiation. Still, without any lenses or optics whatsoever, this lash-up experiment was able to "see" people across the room, a distance of about thirty or forty feet, when they stood in a doorway. Of course, because of the long integration time required to produce a usable signal, they had to stand there for as long as a minute. Years later someone configured two pyroelectric elements side-by-side and connected them differentially, placing an array of Fresnel lenses in front of the detectors so each one saw the same scene from a slightly different point of view. Thus, when anything moved in the scene, slightly different images were presented to the two detectors and they produced a differential output as long as the object continued to move. Voila! The passive infra-red (PIR) motion detector was born. There are millions in use today, so it is pretty easy to obtain a pyroelectric detector element dirt cheap.
At about that same time era, a company in New England (a hot-bed of electro-optics development) developed a dual-band (3 to 5 and 8 to 12 μm) video camera that produced standard NTSC monochrome video using two detectors, HgCdTe for 8 to 12 μm, and InSb (indium antimonide) for 3 to 5 μm. This was accomplished by producing a raster-scanned image of the area the camera "saw" by using high-speed galvanometer mirrors. The horizontal scan occurred at just half the NTSC line rate, so each line was digitized, the pixel values stored in a shift register, and then read out twice to satisfy the NTSC timing requirements. You could select which infrared image you wanted to see with a switch. I developed a high-speed video switch that alternated the video output from the two infrared channels into a single video stream so you could see images from both infrared bands simultaneously, interlaced on the monitor screen. This could arguably be called the first example of multi-spectral imaging, but it didn't stop there. It went much farther. But that's another story...
The government (and others) routinely measure the infra-red heat signature of a lot of common objects to build up a catalog for automatic image processing and, in the case of weapon systems, automatic targeting and tracking controls. All this is made possible by the development of those itty, bitty, incredibly fast, computer chips and similar technologies that have evolved over the last fifty years to allow more advanced video games to be built. Aliens helped hardly at all.
