Well this is fast. Just today we posted about Nautilus (upstream too, not just Elementary) getting Zeitgeist integration and a prototype (already functional) of the "Open file dialog" and "Search dialog" was already created by Seif Lotfy:
For now there's no way to install this prototype, but if the feedback is positive, the code might be released with the next Zeitgeist version. This might not be the way Zeitgeist will be implemented into Nautilus, but who knows, we might see it in Nautilus Elementary (fingers crossed!).
So what do you think? Don't forget to also give feedback to Seif Lotfy.