Done it!
Uses Night-eye shader switcher OBSE plug-in.
Thanks for the heads-up and pointers, Zornac and vtastek!
It seems that Src0 is the unlit screen.
I managed to get more light info from Src1 and so used that for sampling.

Here's the link. It has screenshots:
Detect life effect and Night-eye shader http://tesnexus.com/downloads/file.php?id=36407

• Detect life effect
  
  • doesn't obstruct your view of the actors that you can see and are in the light
    
  • doesn't reveal the type of actor when behind objects
  
  
• Night-eye shader when in interiors:
  
  • applied on post light-processed view rather than the un-lit view as in the normal night-eye shader
    
  • doesn't remove shadow information from your view
  
  
• The default Night-eye shader is used when outdoors.
  
• For the Detect life effect to work, ensure that this is loaded after any other effects mod.

Thanx a big bunch, Kuertee. I likes it a lot. :laugh:

Sorry, I couldn't get back to you. Real life. So you seem to crack it yourself. Awesome.

I installed your mod already. Thanks for this.