Can an iPhone App Detect When A Child Is Suffering Pain Or Depression?

A handful of medical centers are testing a new iPhone app that detects when a patient starts withdrawing from his regular routines and contacts. The idea is that if a person has a chronic medical condition like diabetes or depression, he is more likely to withdraw when in the most pain, so the app alerts caregivers and family members when a situation arises. Does this application violate the privacy of the patient, does it assume the patient is tied to his phone, and is it even accurate?