You increasingly don't get a choice.

Could you explain? Who's preventing you from not installing (or later disabling) anything on your own car?

Law enforcement use them by placing them on cars they are following unbeknownst to the suspect. A jammer is an effective countermeasure.

In the US, SCOTUS did at least rule that they need a warrant for that.

I can't think of anything that meets the hyperbolic claim, but I know some insurance companies have introduced driving monitors to assess how safe your driving is and adjust your premiums accordingly.

Yes, but those are opt ins as far as I know. That is, you agree to have said device installed so you can be eligible for a discount.

Agreeing to have such a device installed and then installing a jammer doesn't strike me as logical.