It only applies to certain microcontrollers, but he provides example Arduino code showing how handy this can be for battery-powered projects.

Very few external components Industry Leading Power Consumption The nRF24L01 represents a breakthrough for coin cell battery operated equipment in the 2.4GHz frequency band. The entire solution ...

Makers, hobbyists and developers looking for a low powered Arduino compatible development board with built-in RF capable of running AVR projects for years using just a single AA battery.