The microchip mrf24j40ma is an 802.15.4 module, with a SPI interface. It's nice and cheap, and it is readily usable on a breadboard, unlike xbee modules. More information here: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en535967 This library provides a basic interface to send and receive packets using plain 802.15.4. beacon mode is not supported.