RFM73P is a GFSK transceiver module operating in the 2.4 GHz ISM frequency band, produced by Hope RF Electronics:

The RFM73P has the following characteristics:

• Low power consumption
• 2 Mb/s air data rate
• Built in packet handling and error detection by CRC coding
• SPI interface
• Support for multiple channels / FIFO
• Relatively small form factor, as shown in the following picture where the RFM73P is connected to the Raspberry Pi:

More information is available in the RFM73P datasheet.