I passed my trigger wire for my aux lights through the hood release cable grommet. There's this other one beside it that looks like it also goes to the cabin. Seems like a lot less involved than going through the firewall.

 

Resurrecting this thread since I could not find any other info on this grommet.

YES!!!

I ran an 8 gauge power wire using this grommet, on the other side is just insulation that you can poke through with a screwdriver easily. Drilled a snug hole for the cable through the grommet and routed the cable from the battery (zip tied to the hood release cable to prevent the cable from rubbing on the fender), down into the fender area, through that grommet and into the cabin. I then used sealant to glue the grommet back in place and seal the cable hole just to be safe.

To access the grommet area you jack the car up for better clearance and remove the pins holding the fender liner in place. Peel back the fender liner and the grommet is right there.