Ford have included an easy way for you to hack into their newer cars. the software platform is called OpenXC. It's open source hardware that lets you get info from the car such as speed, gear, revs and temperature etc. It was developed to help standardise third-party modules, and for hackers to tinker and make their own parts.
A junior engineer from Ford has created a custom gear knob that shows you your current gear, and vibrates when it's time to shift. The case was printed using a MakerBot Thing-O-Matic. He connected an Android tablet and an Arduino, and hacked his way in.
It's a pretty cool idea, and it shows what Ford's OpenXC is capable of. The entire build including source code is available from the OpenXC website.