GeoTracker is a Mac OS X program that is able to plot the path packets travel over the internet from one host to another. GeoTracker uses the builtin traceroute program to determine the ip addresses of all the machines that lay between the source and target machine and the then queries the server from the Cooperative Association for Internet Data Analysis (caida.org) to determine the approximate GPS coordinates of the machines that appear along the path. Please note that the accuracy of the search is entirely determined by the NetGeo project at CAIDA and the information may be out of date.
For more information about GeoTracker check out my Project Page