I used to work for a company that would put temporary cameras out to record particular intersections or stretches of road. It was all temporary traffic safety studies, not an active search or dragnet surveillance, so my conscience was mostly clean. It was still wild to see how much technology can be quickly put out to record and track drivers.

On top of cameras we had Bluetooth sniffers that would get put up on every leg of a 4way intersection and just collect Bluetooth hardware addresses. It doesn't identify you, but it is able to tell which direction you took at that 4 way because your Bluetooth address only showed up on two of the boxes.

One of the more surprising methods for hiding cameras were those big orange traffic barrels. When they stack on top of each other, there's a 6-8in gap between the tops where you can stash stuff. If you ever see two of those barrels stacked on each other, look for a little window cut out near the top of the top one. There might be a camera sitting on top of the bottom barrel and hidden by the top barrel. They'd point it to capture back license plates, so you don't see it when driving towards it.