I’m not sure if you are aware of a web based service known as speedtest.net which allows you to test internet speed. Well, they have now come up with an app for testing internet speed on iPhone.
The app is light on iPhone resources and is user friendly as well. The best part is that the interface has no advertisements. To check the internet speed, all you need to do is get the app from ITunes, install it on your iPhone and launch the app to check the upload and download speeds. The results that you get from this app are highly accurate.