>That aren't detectable? Of course. How do you detect or protect against when the FBI/NSA/three-letter-agency has a warrant for your cellphone (or Google, car,

>That aren't detectable? Of course. How do you detect or protect against when the FBI/NSA/three-letter-agency has a warrant for your cellphone (or Google, car, local coffee shop cameras, Ring cameras, credit card, etc.) information alongside a gag order? How often do you check your cars undercarriage for GPS monitors? Do you know how many times your car has been imaged by a license plate camera recently? Again, I'm not saying that this technology is useless. It's just a lot worse, on several dimensions, than technology that is already invading your privacy this second. If this technology was seriously beginning to be used to track people, a handful of people can thwart it by carrying around an air filter and shaking it every now and again.