Update: There’s a better uptime tracking and connection / downloading speed monitor tool to test the responsiveness of your website, it’s Host Tracker. But be prepared that it may consume quite some MBs of bandwidth of your server because it sends HTTP requests from well over half a hundred places around the world.
Update: Yet another better hosting server / website responsiveness / loading speed test tool: http://www.hyperspin.com/en/quicktest.php
Internet Supervision accepts your web site URL, tests and loads it from 7 major cities around the world: Washington, DC, Los Angeles, CA, Beijing, China, Detroit, MI, Chicago, IL, Gloucester, UK and Sydney, Australia.
It gives you an average downloading speed in kbps and the time in seconds to download the specified web page from each of the locations. A decent international host should in my opinion, score at least 150kbps in downloading speed.
Update: Another good uptime / connection speed test tool to check the loading speec of your website is Alertra Spot Check.