Wired: This Gadget Hacks GM Cars to Locate, Unlock, and Start Them

"GM’s Onstar service offers some of the most futuristic features on any connected car, including the ability to locate the vehicle, unlock it, and even start its ignition—all from a smartphone app. But if a hacker like Samy Kamkar has hidden a small, $100 box anywhere on your Onstar-equipped car or truck, those same conveniences could fall into unintended hands."

https://www.wired.com/2015/07/gadget-hacks-gm-cars-locate-unlock-start/