The GPS positioning data (at minimum) is used by law enforcement today. The GPS tracking in Aaron Hernadez' smart phone and from is rental car were used to put him at the crime scene and put him in the vehicle that was at the crime scene. Seems maybe they found a gun or brass in the car?
Making all this sensor data useful is what a lot of the talk about "big data" is about. Between your smartphone, blackbox in your car, credit card receipts, other? - you won't be able to take a leak without leaving footprints in sensors somewhere.
True!
Most coffee shops and other retailers have those cameras at the checkout.
Those cameras are perfectly reasonable to deter thieves, and help catch criminals. But only as a standalone distinct system
The problem is when all of these systems are linked to create a 100% surveilance system operated by the Government.
If the Government wants to know what I did last Saturday morning, all they have to do is ask!