If you're building a Raspberry Pi project and need to send data back-and-forth, the WiFi module built into newer Pi's should be fine for most cases.
However, WiFi does not have a long range and also requires both investment (through your ISP) and setup (routers, access points, network security schemes).
If you're deploying your project somewhere more remotely, without WiFi or a strong cellular network, like a farm, you'll need another option. Something that can be deployed quickly with no overhead setup and that will transmit/receive over a long distance.
By sacrificing transmit speed and the amount of data which you're able to send, packet radios can transmit much farther than Bluetooth Low-Energy and WiFi.
This makes using a radio perfect for scenarios where your project would need to periodically transmit sensor and/or device data (such as the Pi's battery life) over a long distance. The RFM69 module can transmit up to 50m and the RFM9x module can send packets up to 2km over LoRa and even further using LoRaWAN!
Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM
Raspberry Pi Zero - Version 1.3
All-in-One
The Adafruit LoRa Radio Bonnet for Raspberry Pi sets you up with a RFM95W Radio Module, a 128x32 OLED display and three push-buttons for LoRa and LoRaWAN experiments.
Adafruit LoRa Radio Bonnet with OLED - RFM95W @ 915MHz
There's also a 433MHz version which uses the amateur or license-free ISM band (ITU "Europe" license-free ISM or ITU "American" amateur with limitations).
Adafruit LoRa Radio Bonnet RFM96W @ 433MHz
You'll need a way to access the GPIO (pins) from the Raspberry Pi. The T-Cobbler plus is a plug-and-play breakout which works with almost every new Raspberry Pi variation.
Assembled Pi T-Cobbler Plus - GPIO Breakout
The Pi setup used for this guide is operated as a headless Pi. This means that no monitor is plugged into the Pi and we control it over SSH. We'll add a small display to monitor and interact with the code.
Monochrome 128x32 I2C OLED graphic display
The RFM9x LoRa comes in two different frequencies - 868/915MHz and 433MHz. It can broadcast over LoRa (longer range than the RFM69HCW) and LoRaWAN (even longer range to gateways).
Adafruit RFM95W LoRa Radio Transceiver Breakout - 868 or 915 MHz
There's also a 433MHz version which uses the amateur or license-free ISM band (ITU "Europe" license-free ISM or ITU "American" amateur with limitations).
If you don't have these parts already, grab them from the Adafruit store:
