The posted pdf to the manual shows a little bit of the device. But here's another larger and more advanced device (linked in the article). It is doing the same but with an more elaborated output visualization.

https://www.youtube.com/watch?v=bt3ecnqdUCo

You can clearly see the output in the video.

It only tells you if there are people inside, either moving or breathing, and how far away they are. There's only text output, no actual images.

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From the manual: "RANGE-R is designed for simple one-handed operation. Holding RANGE-R to a wall, door or other building structure, the operator simultaneously presses buttons on the sensor’s two sides to begin the analysis. Within three seconds, the system returns a range-to-target result as well as the status of the target, which is indicated as either a mover (Mov) or a breather (Br). The result is displayed to the user in terms of distance in feet to the target on the unit’s LCD. RANGE-R is also capable of detecting and displaying the range of multiple targets. In such cases, the display will alternate through the different ranges of the targets."

Manual: http://www.range-r.com/documents/RANGER.PDF