Peter Sullivan and I are driving around Palo Alto, California, in his black Tesla Roadster when the clicking begins. The $2,500 German-made instrument resting in my lap is picking up electromagnetic fields (EMFs) from a nearby cell tower. As we follow a procession of BMWs and Priuses into the parking lot of Henry M. Gunn High School, the clicking crescendos into a roar of static. “I can feel it right here,” Sullivan says, wincing as he massages his forehead. The last time he visited the tower, he tells me, it took him three days to recover.