DO NOT BUY
This is a Blender Addon that allows you to add automatically Handles to a Bendy Bone.
Once installed you just need to select the bone and type ctrl-shift-b.
Here's an excellent explanation of how handles work and how to add them manually: https://vimeo.com/181807778
The addon also adds drivers so you can scale the bone by scaling the handles.
Small demo: https://youtu.be/qYs3En7ihL0
Pay what you want: