Functionalities :
_ decode snoop & HCI packet format into a readable JSON format
_ filter HCI packets
_ start/stop Bluetooth scan
_ activate/deactivate Bluetooth
_ reset snoop log file (for Android 4.4 & 5.X only)

On Android K and L you don't need to have developer options activated to use this application
On Android M to activate and/or reset snoop log file you have to toggle Bluetooth HCI snoop log in developer options

Github : https://github.com/bertrandmartel/hci-debugger
This application is released under GPLv3 license