Chronologically it's the other way around I think: Vimium was inspired by the Firefox plugins Vimperator and Pentadactyl.

(The one I mentioned, VimFx, is more recent and more minimalistic that either Vimperator or Pentadactyl.)

There are several; vimperator has been around since before chrome even existed.

You're kidding right? Vimperator and the much better fork Pentadactyl have been around for years on Firefox, and implement everything Vimium does and more, in a much more reliable way. Every single control interface is available, and scriptable in Pentadactyl.

Vimium isn't even the best vimperator clone for Chrome - cVim has now taken that crown by a very large margin, and is worlds better in terms of features, configuration and reliability.