What about a real time WPM indicator?

This will give you the speed you are typing at while you are typing.

Some of typing test websites that Shai suggested have a WPM indicator e.g ;

http://www.freetypinggame.net/free-typing-test.asp

http://www.siteuri.ro/dvorak/contester.php

I think that would be a brilliant idea, and it does NOT distract me as I type.