Digital IO Line Passing with XBee

All XBee 802.15.4 RF family of modules from Digi International have the ability to perform digital I/O line passing. This feature enables the user to toggle the state of any DIO pin on a transmitting radio and have that same pin on one or more receiving radios toggle their state to match the change without any additional hardware. This functionality is an easy way to wirelessly control relays or any other switched equipment.

See also:
https://www.digi.com/blog/xbee-tech-tip-digital-io-line-passing-with-xbee/
https://www.digi.com/support/knowledge-base/xbee-802-15-4-digital-input-output-line-passing