Vehicle telematics and third-party data brokers.
As Admin rightly pointed out, the NSA hoovers up anything that can be hoovered up. But, on the non-spook side of the fence, the average monger probably has more to fear from third-party data brokers than they do from LE. Here's why:
Most LE agencies have contracts with third-party data brokers. Usually there's a website with a login and a LEO or analyst can plug in whatever info they have and do a search. But the agency has to pay for access, so some agencies may place constraints such that the system can't be used for unlimited fishing expeditions. Others may ask their people to go easy on the searches as it gets closer to the end of the fiscal year. But, even if not, nothing in any third-party database meets the evidentiary standard that would allow it to be used in court. Instead, LE treats such info as leads, requiring follow-up that usually requires obtaining a Grand Jury subpoena. GJ subpoenas are only issued in furtherance of felony investigations. Which means, as I wrote in an earlier post, you'll be fine as long as you steer well-clear of anything that even smells like trafficking. Always remember that LE tries to stretch the definition of trafficking to cover as much of garden-variety prostitution as possible. You can't assume or become complacent in any way.
BUT, the restrictions that apply to LE very notably do NOT apply to divorce lawyers and private investigators. They also have subscriptions to the data brokers and, while they may not be able get as much info as LE, they can still get a lot. Consider, for example (depending on the state), that the car you drive is considered community property. That means the wife has an interest in knowing where that car has been. A good divorce lawyer could easily write up a justification to convince a judge. For example, the husband is suspected of shielding assets and the wife needs to know if the car has visited banks or other financial establishments at which the husband hasn't declared any active accounts. Or, in states where extramarital activity is deemed relevant, the car being driven to hotels or unknown residences can be a big problem. As I sit here thinking about it, I wouldn't be surprised if these matters were addressed during the discovery / financial disclosure process. The husband might be presented with a consent form, or the judge could simply issue an order allowing it.
For anyone with a low-tech wife or SO, that's great unless she hires a high-tech PI or divorce lawyer. Everyone can assess their own situation, but the purpose of this post is to point out the scourge of third-party data brokers. They operate (IMO) on the fringes of legal privacy protections. But their business model is to gather, package, and sell as much sensitive information as they can. For every additional data point that's created about you, there's a buyer standing ready. Here's the website of just a single company that specializes in vehicle data:
[URL]https://ims.tech/vdx/[/URL]
P.S. If you think you have a vehicle telematics system with a simple on-off switch, I would encourage you to research your specific brand and model. I think most will be shocked at the info collected, uploaded, and stored. And even more shocked at the difficulty, or impossibility, of shutting down the flow.