You should have been /be creeped out by on-star if anything. Every on-star vehicle can be tracked within the triangulation limits of cell towers (aka. within half a mile if not better.)
I did this on my father's 2008 GMC Sierra and we replaced it with a BlueStar[1] bluetooth adapter. It works flawlessly and mimics OnStar functionality down to muting the radio and stopping A/C fans for voice control. It's far nicer than most aftermarket Bluetooth mods.