Ford Sync is Windows CE Based, so to use most of the SDK features, you will probably require Visual Studio 2005 or greater.
Here is a snippet from Ford regarding the features and functions of the Ford SYNC SDK
Ford is hard at work developing an API to allow developers to integrate their Smartphone applications with SYNC. The Developer Program website will educate developers about the Ford SYNC platform and how to interact with it via the API. There will be a full set of documentation, example applications, reference libraries, and even a developer forum so you can reach out to the community for quick help.
With the available SYNC API's, mobile application developers will be able to do some of the following:
1. Create a voice UI for your application using the in-vehicle speech recognition system.
2. Write information to the radio head display or in-vehicle touchscreen
3. Speak text using text-to-speech engine.
4. Use the in-vehicle menu system to provide commands or options for your mobile application
5. Get button presses from the radio and steering wheel controls.
6. Receive vehicle data (speed, GPS location, fuel economy, etc.)
The official API and full website launch is set to be targeted for later this year.