I've made available both C source code and binary executables for a
program that reads telemetry transmitted as UDP datagrams from an
instance of the X-Plane flight simulator (
http://www.x-plane.com) and
emits a continuously refreshed KML file that Google Earth can ingest
to create a dynamic "moving map" display. The code should be
relatively easy to port to other flight simulators or entirely
different types of applications that transmit geographical coordinates
via the Internet Protocol.
Source and binaries are available at http://www.chriskern.net/code/xplaneToGoogleEarth.html
along with instructions on how to configure the three coactive
applications.