Do you have information on professional detection equipment?

Detection apps are known to be ineffective. It's mostly because IMSI catchers comply with the standard. Your baseband will fall for that - there's not much useful information to be passed to the operating system - or even an app.

Most firms who sell lawfull interception appliances also sell the appliances required to protect, detect or mitigate against it. Usually they only sell their appliances to law enforcement, the militairy and intelligence agencies after signing a NDA. The legality is often dubious, and atleast some are nothing but a expensive user friendly box around GNU radio, osmocom and very little code of their own. ( But my knowledge could be dated. ) If you so desire mail me for a list of names, but i'd rather not post them here connected to my identity.

I won't contact you in that matter. I get an idea from what you've said, thank you.

While the idea behind the app is great, that one specifically is abandoned and should be considered non-working.

I have struggled to come up with a way of asking this neutrally, and I believe in a right to privacy and think "nothing to hide, nothing to fear" is nonsense, but seriously... wtf are people doing that they are "sincerely concerned about stingray devices"?

The article mentions attending protests as one such "suspicious" activity.

They live in areas with crime. And don't want to get their phones picked up in others' investigations.

Probably reading articles about the massive proliferation of private and State Stingrays...