According to UWINLOC, a French, Toulouse-based company, it is possible to install battery-less beacons that capture energy from a radio field. At the core of this technology lays a basic principle: very small devices require extremely low power.
The beacons harvest radio energy through miniaturized antennae. Once the internal energy storage system goes beyond a specific level dubbed as “charged”, the devices start to emit a “ping”. It is this ping that enables the location in a 3D space. Several carefully-placed receivers locate the position of the beacon.
The small devices are packaged as tags that can be attached to any object. I see great potential in such a technology. It is a bit scary, but it might open the door to free energy. All it takes is to balance the power requirements of a device with its capacity of harvesting energy from the electromagnetic/radio field.