That's not true. Read up on Katz V United States. A wiretap was placed on a line that connected to a phone booth. No physical intrusion happened at the phone booth, and the phone booth was not owned by the person using it. But SCOTUS ruled that when the user closed the door, he had an expectation of privacy that his conversation would not be heard by anyone but the intended recipient.

That's true, but the analogy you drew was to Jones, arguing that if the police cannot place a GPS unit on a car without a warrant the same must apply to obtaining GPS information through another means. That is untrue.

And since we're going with snide "read up on this case", how about you read the more recent Miller case or Maryland v. Smith before being a condescending dick?

I obviously have that same expectation of privacy when carrying a device that I own for my own purposes. All of the data coming from it, whether it's my conversation, my email, texts, or location data, all of it is personal information not to be shared unless I expressly allow such sharing by contract or EULA

Read your EULA, the cell phone company is clear that it keeps records of data sent, and GPS information. The third-party doctrine cases (post-Katz, mind you, so still good law) have been clear that information given willingly to a business is not protected by the fourth amendment against the government getting that information from the business.

Doubly true in this case, since the company is also what generates the information.

The fact that this method is easily detectable makes the difference. You are not expecting privacy when you see someone following you

Not are you (reasonably) expecting privacy in information possessed by Verizon or AT&T. Which is what we're talking about.

If you're accepting (as you must) that the same information can be protected, or not, by the fourth amendment depending on how it is being obtained, you can't make a "GPS attached to the car = GPS information kept by your cell phone provider" argument.

So let's discuss the actual legal issue.

If they choose to share it with someone else, that's your fault, you trusted the wrong person

Which also applies to information shared with a cell phone company. You either need to distinguish Miller or argue why the third-party doctrine would apply to bank records held by the bank but not cell phone records held by Verizon.

They have not changed the method as you previously stated, they just changed the device from one that they own to one that you own.

And changed the chain of custody from "we intruded on to the person's property to place this device which transmits information to us" to "the person gave the information willingly to a third-party from which we received the information."

Which is also the difference between a listening device and my girlfriend wearing a wire when she comes to see me (see United States v. Hoffa). That's actually literally the same means, the only difference is that the recording is being done by someone who is not herself a police officer. And since Hoffa, Miller, and Smith, are all post-Katz you still need to deal with them.

It is the same technology, the difference is that the cell-phone data is given (by the consumer) to Verizon which then gives it to the government, as opposed to the government taking the data directly.

The intermediary step is the difference. Hence Hoffa.

With a subpoena, which is has to be gotten from a judge the same as a warrant

No, it doesn't. A subpoena is not subject to warrant requirements, much less required to be supported by probable cause. You claim to have been a PI, but I'd really hope a PI would be aware that subpoenas aren't required to meet any evidentiary requirements.

Cops just can't walk in to a business and say "Give me all your records that have anything to do with John Doe"

Well, they can, they just can't enforce it. If the company voluntarily complies, there's no fourth amendment protection for Doe to invoke.

And if they obtain a subpoena, Doe has no fourth amendment protection.

But let's say the police don't, and just take the data. The only entity whose rights have been violated is the company, Doe still has no fourth amendment protection.

There is no situation where the records of Doe's cell phone GPS (held by the business) would require a warrant to obtain from the business.

Unless you're claiming the third-party doctrine doesn't apply to cell phone service.