Jonathan Swift’s smartphone

Evolution has engineered us for social interaction. Our bodies are instruments exquisitelytuned for tracking and measuringthe auras of others. In quantifying ourselves, therefore, we also quantify those around us. This is the insight that underpins the brilliant new iPhone app pplkpr.

Connected to a sensor-equipped smartwristband, pplkpr takes biometric readings of how interactions with your Facebook friends, in person or screen-mediated, affect your physical and emotional state. pplkpr tells...