Its a Business ISP in Canada called Network Connection (connection.ca), we deal mostly with small to large businesses and provide them with DSL, web hosting etc. But the problem is becoming now that our customers would like to know their speeds and we have no qualms in telling them what they are getting but they always go to speedtest.net and that thing is hugely inaccurate. At the moment for testing purposes the server we are running is a Debain (Lenny) server with Apache. It works fine with the previous speed tests I've installed and run but alas they were no good. It really is like searching for a needle in a hay stack! Apart from the one you have coded have you come across any others?
We would redirect them but then it leads into well if speedtest.net is no good why is this one and why don't you have one of your own? Its a pain that way.