Display / Show products based on customer group

Is there such an extension that exists already that shows products based on the customer group? So if you are a member of a certain customer group you might have certain products hidden and others shown when logged in?

I've had a look in the extensions directory but couldn't find anything and before I create one I thought it best to ask

Ta

There is This Extension which is compatible with both v1.4.9 and v1.5

Thanks, it's close but not quite what I'm after as I want all the categories to be the same and don't really want to have to duplicate them, just swap what products appear in those categories if a certain customer group is logged in. Who's site is that out of interest?

Any others out there?

Thanks

Just noticed it's Q's new site!