I honestly don't know. Maybe they could equipt them with powerful microphones that can record the conversations of the people below. They would help with putting a stop to thought crime. The police could then use automated speech analysis to determine if you are comiting thought crime and activate the appropriate response.

Afyer the initial reponse they could remove the person and their friends and family from society. It would be a challenging task updating the records to show that these terrorists never existed. You would also need to make sure that the people around are aware that there own memories are wrong.