Apple patents method for live voice mail screening

As described in the document, incoming calls intended for a user's telephone terminal can be routed to a hosted voicemail system if a user does not answer. As a caller is leaving the message, a conference call connection is established between the incoming call, voicemail system and user, thus allowing a user to listen in on the message in real time.

AppleInsider

Not unsimilar to Google Voice's “ListenIn”, but regardless, sign me up for this.