You might want to check out TestGen4Web (http://developer.spikesource.com/wiki/index.php?title=Projects:TestGen4Web) which is a firefox extension for capturing browser activity. You can save your script as xml and then use adapters to change that xml into testcases for testframeworks. There are currently translaters for simpletest (php) and httpunit (java).
That project has an awesome schematic! It seems like an interesting project, and after playing around with several recorders the translation seems very reasonable -- capturing higher-level information than just HTTP requests is useful, and best done at a browser level, but it doesn't need to be that closely attached to the target test framework.
However, like I mentioned in the Selenium comment, this doesn't really feel right for unit testing IMHO, and certainly doesn't work well for TDD.# Ian Bicking