No idea myself, Noam.
And since sylvie says so, it's still missing in tiki 1.9.cvs
You can use, if needed, a program called Dadabik (http://www.dadabik.org/), which makes what you wanted (and I also wanted a year ago), even if it's not integrated within tiki, really.
See what I mean at: http://moviments.net
and press "Demana un correu-e" (ask for an e-mail), and so on. We have denied access to all contents of the records, but it is configurable in many ways. (see at the dadabik homepage: http://www.dadabik.org/index.php?function=show_demo)