The iPhone wouldn’t stop chirping. On a recent morning I was riding in a car through Silicon Valley with three people from a startup called Iotera. A small tracking tag was attached to the passenger-side sun visor. Our mission was to see how far we could drive from Iotera’s office building before the tag would stop transmitting its location to a small base station on the building’s roof—which meant the location-logging app on the phone would go silent.

 

It took several miles. That’s good news for Iotera, which is developing tracking technology that can work throughout cities without requiring access to a commercial wireless network or even a short-range wireless protocol like Bluetooth.