Adafruit (PID 2267 Bluefruit LE Friend - Bluetooth Low Energy (BLE 4.0) - nRF51822 - v3.0

In it's simplest form, it works on the same principle as a common USB/Serial adapter . Any data that you enter via your favorite terminal emulator on your development machine will be transferred over the air to the connected phone or tablet, and vice versa, as a basic 'UART' connection

You might be asking, Hey my macbook already has Bluetooth and I can get a USB Bluetooth adapter, so why use this? Good question! You can get a Bluetooth 4.0 USB dongle from the store already, but Windows 7 doesn't support Bluetooth Low Energy natively, and on Win8 or OS X you'll have to sort through a huge pile of native Bluetooth APIs and development tools that often require an annual paid license and specific license terms to access.

The Bluefruit Friend is much more, it has a full BLE peripheral stack and interface software so that you can treat your BLE connection just like a UART connection - that makes it trivial to use with free Terminal software or scripting software like python (with pySerial).

To use, simply plug into your computer and flip the switch to either UART mode (transparent data transfer, anything you type will be sent, and data from phone is received as well) or CoMmanD mode, where thanks to an easy to learn AT command set, you can also create you own basic GATT Services and Characteristics, simulate Beacons, and change the way that the device name appears/advertises itself.

Update the firmware on your BLE Friend over the air using any BLE-supported iOS or Android device.

As if April 5, 2017 the board has been updated to change the USB-Serial chip to CP2104 and remove the SWD connector (you can get to the SWD connection pads on the bottom of the PCB).