They can track you by putting a camera in the door of any building. Face recognition is good enough to pick anyone out of a group. They already use it in England and have been for 10 years. Those cameras can see you from hundreds of feet away. Interpolate the recognitions and they have your path.

30 feet is not the implantable chips, those are much more powerful transmitters with the most sensitive receivers. Personal chips I believe have 128 bit encryption. Think you can crack that? I'll see you in a thousand years. They can't even break the iTunes encryption and there are far more people working on that.