It has to use some kind of communication medium. Very likely wireless spectrum of some kind. It's likely to be in the millimeter spectrum in order to communicate with very small devices (microwave >50 gigahertz frequencies). Get a CT scan and look for embedded devices inside you. Also get a field strength meter capable of detecting frequencies in the 50-60 Ghz range or even higher. They make specialized equipment capable of locating RF frequencies across wide RF spectrums. Using a directional antenna you can find carrier waves aimed in your direction. Having mentioned all of this, it's only likely they can do this to you when you're in a known position. If you travel outside of the beam, the signal would go away. Good luck.