The RFM12B is a great inexpensive option for wireless communication; it's an ISM band FSK transceiver module implemented with a unique PLL. These modules operate in the 915MHZ band and fully comply with FCC and ETSI regulations.
This module has a wide voltage supply range of 2.2-3.8VDC. An SPI interface is used to send data and configure the RFM12 module. The configuration commands, described in the RF12 IC Datasheet linked below, can be used to set the data rate, frequency band, wake-up timer, transfer data, receive data from the 16-bit FIFO, and much more.
The module comes in a 14-pin SMD package, with pins spaced by 2mm. Check below for a breakout board.
SPI compatible interface
High data rate (up to 115.2 kbps in digital mode)
2.2V-3.8V power supply
Analog and digital RSSI outputs
Differential antenna input
Automatic antenna tuning
16-bit RX data FIFO
PLL and zero IF technology
Fast PLL lock time
High resolution PLL with 2.5KHz step
Programmable TX frequency deviation (from 15 to 240 kHz)
Programmable receiver bandwidth (from 67 to 400 kHz)
Analog and digital signal strength indicator
Internal data filtering and clock recovery
Clock and reset signal output for external MCU use