The Ford Hackathon at Techcrunch Disrupt encouraged use of the Ford SmartDeviceLink (SDL) SDK to talk to their head units. The apps can be submitted to Ford for cars supporting Ford Sync. Toyota also represented itself to lend support to this open source effort. With a combined open source effort the number of cars targetted by such apps could be higher.
The SDK can be useful for insurance applications for measuring ride and driver quality. Many applications were built at the hackathon around this idea.
We built an application to synchronize brakes between two cars in real time to prevent car pileups in low visibility conditions. It alerts the driver that a car ahead acting as a virtual break light. Our goal was distraction free driving, so it used voice commands to alert and automatic brake detection instead of manual brake notification.
A previous SDK also supported by Ford was OpenXC. Another popular SDK at the hackathon was Vin.li SDK.
There was discussion of a Waze like app that is built into cars. Talking to people I learnt of the role the Department of Transportation is playing to bring Intelligent Transportation to reality.