An example, measuring traffic flow in a city.

You can do it with cameras and ID plate detection tools, which allows tracking where anyone is at any time.

You can also put magnetic loops into the roads, which just tells you how many drive over a certain area of the road, without any individualized tracking.

Good telemetry is like the magnetic loops. But nowadays very few implementations are that privacy respecting

Better surveillance: put RFID readers in the road that track the RFID tags in the tires. Then ping that against the database of who bought what tires. People won't known what hit them.

That is true for people with the same level of access as you. The 3 letter agencies have access to much wider array of data and yours can and will be used to track people of interest and those who they deem problematic.

Do you want to be surveilled?

We promise it's anonymized.

Would you mind setting up a 24/7 stream of your bedroom? I don't know you, so technically it's anonymized.