The unofficial Google Earth Blog reports that Google is about to release an API for Google Earth. "The Google Earth COM API is designed to let third party applications query information from and send commands to the Google Earth software. External applications can query the current viewport, control the 3D camera, enable, disable, load KML features, traverse features, and more."
A draft for the API documentation is available here. This small API has been available for awhile, but Google didn't officially support it.