If you are running OS X 10.9 or higher, you can also use the sniffer on OS X using the nrf-ble-sniffer-osx package from Roland King. (Make sure you have the latest version, as of 20 June 2015, which is now compatible with the FTDI chip used on the Adafruit board.)
Setup instructions are available on the wiki page for the project.
Be sure to download Wireshark version 2.0.x NOT the new 2.2.7 that was released June 2017
Please note that there can be a long delay (30-60 seconds) before Wireshark shows up using the tool, due to the X11 startup time, etc.
Last updated on Jun 14, 2017
Published on Nov 19, 2014
If Wireshark doesn't show up and X11 has been installed correctly, try forcing X11 closed and trying a second time. The startup process can sometimes stall.