The RFM69 is the same RF Transceiver Module used on the Talk² Whisper Node. The module is based on the silicon from Semtech SX1231H and has many great features like: 66 bytes FIFO, RSSI, CRC and AES-128 bit hardware encryption. The module can be powered from 1.8V to 3.6V and has an incredible low RX current of only 16mA, or just 0.1µA in sleep mode.
If you wish to build your own hardware to communication with a Talk² Whisper Node, this is the RF transceiver you should use.
915MHz 20dB - RFM69HW-915S2
868MHz 20dB - RFM69HW-868S2
433MHz 20dB - RFM69HW-433S2
All technical details can be found on the datasheet: https://www.hoperf.com/data/upload/portal/20190306/RFM69HW-V1.3%20Datasheet.pdf