Listening to private calls to gain insight in therapy

The New York Times Cases article this week examined how therapists sometimes get an unintended look inside the patient's life, by the phone calls they take. Therapists now find themselves able to gain insight beyond what is said in session, by how patients react to cell phone calls from children, spouses and others.

But I can't help but feel a little odd about this. I know the patient shouldn't expect privacy if they take a call in front of his or her therapist. But is it OK to put those conversations on the analytical table? Should the patient retain some control of what the therapist and patient talk about or should the therapist be free to bring up something that is observed? Maybe they do this already and cell phone calls are just another observation.

This is just one example of how technology is changing clinician-patient communication. What are others?