scene looks different in different cameras?

I wish to implement a hand-held thermal scanner. it’ll be a camera, with a screen, showing the scene in IR/night vision, which the player can raise and lower on front of them.

I can do the camera part rendering to a texture just fine, but I don’t know how to make the scene look different, ideally I’d like something like vertex painting or another hidden property to be used to indicate the temperature, which colors the materials when rendered by my scanner. Hope this describes what I’m after…

Can materials know which camera is rendering them? Any other way to do this effect?