All I can say is OnStar doesn't even compare to Ford's Sync if anyone tries to sell you that Ford has the same thing. We lived in Alaska for a number of years and went to some very remote locations and for giggles we would call OnStar just to see if we could contact. It never failed to reach an operator. We had NO cell service where we were on our cell phones. Sync wouldn't hold a candle to OnStar and has no capabilities like OnStar. It's a bluetooth extension of your phones voice control capability and if your phone battery is dead, you forget your phone at home or you are in a no cell service area, your Sync service is GONE. It uses your phones browser to locate things like restaurants and such. I know this wasn't even asked, but someone did mention sync earlier in the discussion. Again, no comparison.
My wife uses our OnStar all the time. They find her hotel rooms as we travel and connect us to the front desk. They give us directions to the nearest "fill in the blank whatever we are looking for". They diagnose a check engine light and let us know if we should keep driving or find a dealer (which they make the appointment and we get priority when we get there). They have unlocked our doors many times and that is huge if your car is still running. They have set up roadside assistance for us when we have had flats. I love the service. It's like a concierge for whatever you need. I have peace of mind when my wife goes alone halfway across the country because I know she always has a way to reach someone if needed.