[Eric in the Ozarks]

Police radar jammers were once commonly sold in the US.
I don't see them advertised anymore.

[rockrr]

I still have one - packed away somewhere. They’re not particularly valuable now that the po-po are using laser detectors.

I will say that it was a lot of fun to play with ;’)

[Bloody Sam Roberts]

I still use an old Escort radar detector...not a jammer. A lot of police departments still use X and K band guns for speed traps. The old boy has saved my bacon many a time.

[9422WMR]

Just put foil between the hub and the wheel. Instant radar scrambler!/S
That was a scam back in the 80’s. Some people tried it!
Now I’m sure there is an Electrical Engineer out there that knows how to create a short range scrambling device that disrupts cell phone signal.
I would love to have one of those pocket cell phone signal scramblers. I could go out to dinner with my family and the kids would not be distracted by their phones.
I know, just a wish of something that will never be.....