Battery-free smart home sensors are smaller than a penny

Researchers have created small metal tags that can signal when a door or drawer is opened, count reps in the gym, or even track bathroom use for elderly relatives.

Most smart home devices require power one way or another. You have to plug them in, recharge them, or replace their batteries at some point.

Georgia Tech researchers think they have a better way.

Their new tags are battery-free, quiet, inherently private, and cost only a few cents ...