I'm sure to a lot of older people that probably seems like a great service. "Never lock your keys in your car again!!!" I'm sure the advertisements say (notice the three exclamation points). If my car had that service it would freak me the hell out! You're telling me someone can remotely unlock my car from anywhere in the world? How secure is that? Everything everywhere has been hacked by someone. I don't even want to think about what would happen if that service got hacked.
Even if you assume it's fool proof and only certified OnStar employees can utilize it, what happens if some lazy employee fat fingers some number. Instead of unlocking car #12345 he unlocks car #12346 and that happens to be your car that's sitting unattended at the airport for a week (with all your valuables in it).
What else can they do remotely? Without you knowing? Scary!
Update: Q2. Can OnStar really unlock my vehicle from a thousand kilometers away?
A2. Yes. Simply call OnStar at 1.888.4.ONSTAR (1.888.466.7827) and give the Advisor your PIN and account number. OnStar can delay opening your door for up to 15 minutes, giving you enough time to return to your vehicle. OnStar Info