ZigBee is a protocol that works on the 802.15.4 spectrum (WiFi is also known as 802.11 for its slice of spectrum.) As a short-range, low-power protocol, ZigBee is suited for two-way communications among small devices, and can be used to build self-organizing networks of devices.

FORBES: The Wireless Boom That Won't Need Us

The ZigBee wireless protocol was designed as a cheaper and lower-power alternative to Bluetooth and Wi-Fi for embedding in lighting switches, thermostats, smoke detectors and other sensors.

ECONOMIST: The much-talked-of smart grid prepares to enter the home