jason jason....
Simply being able to have the doors unlocked remotely is worth having Onstar.
On the other hand, my car has one of those remote control gizmos. Recently while Christmas shopping I loaded my packages, and my KEYS into the trunk. Standing there like an @$$ with my cell phone, locked car, and nothing else, I started walking back to the mall. I called my sister (my emergency key set holder) hoping that she'd come rescue me. She said I'll unlock it right now for you, go back to your car!! Relieved, thinking she was at the mall also, I walked back to my car, still talking to her. I get to the car, wondering where she is, when she says "aim your phone at the car." I thought she was nuts, but I'd humor her anyway. As soon as I put my phone near the car all the doors unlocked! She told me about the article she had read about using your key fob over a cell phone. I'm glad she had paid attention to that article. I don't think I would have read OR believed it.