You could also possibly look at connecting to route servers located around the world and grabbing down the response times from there. You could use Time::HiRes for fun.. Take a look at these two programs that me and my co-worker wrote for some inspiration and also see http://traceroute.org for a list of route servers. You could basically combine these two programs into one and get a decent idea of what's going. You'll need to account for connectivity between you and the route server cuz all timing will be dnoe locally.
-brad..