Capricorn, they are close to the chipping concept, when the first thing they do is get cell phone records, and tie those call records, GPS, and cell phone towers. Many crimes have been solved using those records to connect someone to a crime. Any system can get tricked or hacked, or just a glich can make it fail, but in theory it would work. The assumption like you say would be everyone had one, and they were never messed with, so it sounds foolproof. It also sounds foolproof to advocate just taking away all the guns from everyone.
Point being, the same bad guys will mess with either avenue, and all the good guys will go along with either avenue. In the end, you only give another advantage to all the criminals, when you disarm all of us.
No At1, there is no simple answer for a solution. We just bark up the wrong tree, and nobody knows what the right tree is. It sounds simple when you hear an Adam Lanza, was a recluse in his room, had mental issues, and was obsessed with violent video games. Wow, that sounds like every other kid on the block. So who are considered those who could potentially murder? You would think that the worst gang member in the inner city, with poor grades, poverty, would be the one to do these things, but it seems to be affluent, good kids, in areas you would never imagine. Nice quiet Colorado neighborhoods, New England.