DIfferent Material Nodes on different Cameras / FLIR

Hi Folks,

I hope this is the right category to ask a question like the following.
Lets say I have 2 Cameras. On is connected to the first person char and the other is a 2D Scene Capture, connected to a FLIR, the fps is carrying in his hands. And lets say, the image the 2DSceneCapture is seeing is rendered to a Render Target, displayed on like a Display on that FLIR.
The information, how “hot” a part of an object is, is stored in an dynamic Render Target inside its Material Instance and this Information should be used to do the heatDisplay Magic in the FLIR.

I am not sure, how I could archive that.
Should I go with s.th. like building a switch inside a Material deciding if the Material is rendered in the FPS or in the Flir Camera. Is s.th. like that even possible?

Or should I go via PostProcessing, but how do I get the HeatInformation of an object into an PostProcessing Material?

How would you guys approach something like that?

Any hint would be really appreciated!

Best regards,

DonBasti