An article in the Wall Street Journal details a new business in Toronto that has placed WiFi sensors in major shopping and nightlife districts of the city. The sensors grab WiFi data from passing smartphones and builds profiles of what people are doing and where they are going. The data is sold to local businesses, who also allow the sensors to be placed inside their businesses. It is an interesting innovation, but has some troubling prospects for privacy. As we carry around our smartphones, tablets, and laptops, the MAC addresses in each of them provide a unique identifier for this kind of data collection. Once this kind of data is known to exist, it can be subpoenaed for civil and criminal investigations. And the government could use it as part of an investigation into your habits and whereabouts.
Maybe an Indiegogo-funded Faraday cage wallet for smartphones would be a good idea.