Stingrays are dangerous, but they don't even need them. In the US our cellular providers are directly accessible by the government without a warrant or probable cause. They get IMSI logs immediately, and they can triangulate off of that alone. This is far worse than a device which anyone could detect using software on their phone.

Stingrays were used extensively by the US in the middle east for service disruption (jamming bombs triggered by cellular) and for targeted assassinations (our missiles lock directly onto the cellphone after the target is identified). Fun stuff! Coming to a place near you!