The answer, of course, is Agitar's webcast titled Turbo-Charged TDD with Agitator. (I'll let you figure out why on your own ;)

There was a bit of a demo effect (and latency issues, although I avoided the latency problems by watching the recording just now) and there really wasn't much said about TDD, but the webcast did a good job demonstrating what Agitator is all about.

I can't say that I'm convinced of Agitator's value but I would be interested in hearing about first-hand experiences with the tool...