This story reminded me to write about the future.
It's a four-stage process: Data gathering, data interpretation, communication advice and response modification.
In stage one the optical, audio and chemosensors gather information about the user and other persons present.
In stage two the information is translated into likely emotional states or intents.
In stage three these states can be communicated to the user via visual (a change of tint in the corner of the eye if glasses are worn, for example), audio (tones can give info or warnings) or physical (it can prod those who can neither see nor hear).
In stage four, the response of the user is modified, if necessary, by directly stimulating vocal and smile muscles or using medication or perhaps some as-yet undiscovered NLP or hypnotic technique.
The device can also be employed to inform the user of their own apparent emotional state as this is not always the same as the emotion that is being felt internally at the time (for example with autistic populations).
One can only speculate as to how these technologies might impact on privacy and safety? Chemosensors, night vision and ultra acute microphones are a stalkers' delight!
Which brings us back to dogs. If you want to hunt people, that's what dogs are for ;)