Is it possible to make a listener for light?

[GreyyWall]

So my friend makes all of our friends custom character mods and the caves update broke a part of mine where it listened for the time of day so I was wondering if anyone knows how to listen for the light level (if there even is such a thing) that the character is in? If so would it be triggered by only the character being played or by all characters on the server?

[Mobbstar]

Isn't there a lightwatcher component? Wilson reacts to being in the dark, after all. So does the Grue.