Lol, to be fair, it was kind of subtle... I read it and was like "Nah, he can't mean that! A Geiger counter is a thing!"

I bought a cheap one that plugs into a phones headphone jack, back when phones had those! I'm sure it wasn't accurate enough to mean much, but it definitely worked! I bought some uranium ore on Amazon to test it out!

There absolutely are devices like this, I believe the person you replied to was being sarcastic.