2.4GHz transceiver modules with built in antenna designed around the Nordic Semiconductor nRF2401A with high sensitivity and good range.
These units are a SparkFun exclusive, all images are theirs.
The Data Ready pin must be connected to a compatible InterruptIn pin. see http://mbed.org/handbook/InterruptIn for details.
Currently only Shock Burst mode is supported.
Example project: Space invaders with wireless controller