Cell phones are tracking devices that make phone calls. It’s sad, but it’s true. Which means software solutions don’t always matter. You can have a secure set of tools on your phone, but it doesn’t change the fact that your phone tracks everywhere you go. And the police can potentially push updates onto your phone that backdoor it and allow it to be turned into a microphone remotely, and do other stuff like that. The police can identify everybody at a protest by bringing in a device called an IMSI catcher. It’s a fake cell phone tower that can be built for 1500 bucks. And once nearby, everybody’s cell phones will automatically jump onto the tower, and if the phone’s unique identifier is exposed, all the police have to do is go to the phone company and ask for their information.
http://nplusonemag.com/leave-your-cellphone-at-home