I was reading about Google's "cost-per-action advertising program" ... is this some thing that is available only through Adsense? I couldnt see anything in my adword campaign ...

I was reading about Google's "cost-per-action advertising program" ... is this some thing that is available only through Adsense? I couldnt see anything in my adword campaign ...
Currently it is invite-only for certain adsense publishers.