Module identification? (2007 Impala)

[nekrostatic]

Hey all! New member here, going to have a few W-body specific questions as I head into an LS4 swap.

I spent most of today pulling the harness out a 2007 Chevy Impala SS. I THINK I have everything that I need, but when I was tossing dash parts into the trunk, I saw a module located on the driver's side behind the felt, near the tail light. Does anyone know what it is? I forgot to get a part number off of it. 

[digitaloutsider]

That's usually where the OnStar box is located. Anything you need powertrain related should be in the engine bay. I don't recall if these need a BCM to work or not or if there is a separate TCM for them, I'm not super versed in the LS stuff in a W car.