camera - adjust lens and dolly in opposing directions

I've seen this in 2 applications, but I'm sure it's in more, and it's Great. Showcase and Bunkspeed Shot has it from what I've seen.

It's basically a live push/pull, dolly zoom, vertigo effect. Call it what you want, but those are a few common ones I've heard.
It allows you to keep the same basic framing of your shot, but adjust the perspective of the entire image. So it seems the camera isn't moving, but really it's moving in/out while zooming out/in at the same time. So your subject stays put, but it's perspective changes.

I couldn't find a script for it here.
Anyone? I figured this would be a pretty easy one, or I probably just couldn't find it.