TalkBack is more than an answering machine, it's an interactive messaging device that allows you to respond to your voice mail messages as you receive and listen to them rather than after you've listened and forgotten them. The system analyzes the waveform of the message and makes some inferences about content based on patterns in the waveform.

Long breaks are assumed to be turn markers or discourse segments and a sharp increase then decrease of the wave followed by or preceded by a pause is assumed to be a question. Recording time is inserted between these segments and after questions allowing the person to "converse" with the message as they record their response.

TalkBack website