Yep, did it in my old 05. Did not add one to my 08 and I'll never add one again. I have wired dozens of 12v systems, add-ons and accessories over the years including two world record holding vehicles, one being one of my AVs, and I'll never willingly do another muilti-point alarm in a GM vehicle. The harness spiders into like 25 different sources and is a major PIA.
To each his own, but I wouldn't suggest it. If you are going to, I'd explore it first and make an educated decision on weather or not you actually want to do it.