I used to play games, when kept on hold on the phone, reciting a list of ECHELON trip words. See how many bells you can ring at once.
Check out "celldar", developed years ago by a company called Roke for the UK military. They can track all individuals and vehicles across the landscape, whether or not they're using phones. They can track you inside buildings. They use software developed to detect bodies in avalanches.
It's portrayed at the end of that creepy Batman movie, The Dark Knight. Gotham's cellphone network is turned into a vast radar and surveillance grid.
All of this is small fry to what they plan with 5G.