Planet Extech have a FLIR camera. That's a camera that does fancy thermal imaging. In other words, yeah, it's how the Predator can see stuff, and it's also how you're going to see some great pictures of the PS4 and Xbox One.
The site had a goal in taking these images: they wanted to show the heat distribution on both consoles, as well as tracking how hot various components got after use. Seems in their testing they found the PS4 to get hotter - around 30 degrees Fahrenheit at one point - but then given the PS4's power supply is internal, while the Xbox One has a separate power brick, that's to be expected.
As anyone with a PC can tell you, no temperature recorded at any point here is anything to worry about.
I've included a few pics here (XB1 on the left, with the top image the XB1's Kinect, PS4 on the right), but the full galleries can be found at Extech.
NOTE: Sorry, I should point out that the images in this post aren't direct "comparison" shots between the consoles. I simply picked the best images to highlight here, not ones directly comparing temperatures at certain run times.
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Xbox One Thermal Images [Planet Extech]
Playstation 4 Thermal Images [Planet Extech]