Have Onstar? Will Hack

 At this year's White Hat convention, someone hacked an OnStar car using a cell phone and sending text messages.  The person was able to unlock the doors and start the car.

Now, as bad as this sounds (and it's pretty bad) the same type of technology is used for things like smart grids.

http://gizmodo.com/5825832/hackers-can-unlock-doors-start-some-cars-via-sms

Paper on Hacking the Smart Grid (PDF)