This Bluefruit LE Friend is programmed with a special firmware image that turns it into an easy to use Bluetooth Low Energy sniffer. You can passively capture data exchanges between two BLE devices, pushing the data into Wireshark, the open source network analysis tool, where you can visualize things on a packet level, with useful descriptors to help you make sense of the values without having to crack open the 2000 page Bluetooth 4.0 Core Specification every time.