The Seek Tool is described in one of the software release notes during the 2.0 beta phase. I think it's in the notes to 2.0 beta 3 or 2.0 beta 11, I don't remember which.

I've been holding off making a FAQ entry for it, because its behavior keeps changing as Toby tweaks it on the way up to 2.0 final. When 2.0 final is out, somebody remind me to get a final FAQ entry put together.