According to the video, there are some control lines that lead back to the cockpit, to winches or line stoppers. Unfortunately, the video doesn't really explain what their purpose is. Presumably, they provide a means to adjust the tension from the cockpit.
I like the simplicity of this concept, but watching the video I wonder how well it works? The jibes they were demonstrating seemed quite a bit faster and forceful than I'd expect with a brake. Also, it annoys me somewhat that I'd still feel the need to use a preventer after spending all that money.
I agree. Installing a boom brake is on my Spring to do list. After looking at SD's installation it seems the Dutchman is the way to go. Two of my biggest concerns were introducing a tripping hazard and being able to have normal boom movement when not downwind. With the Dutchman you can easily release tension from the cockpit and solve those issues. With the Gyb Easy I'm not so sure. Of course the Dutchman is a bit expensive and the Gyb Easy at first look seemed like a cheaper alternative. Either way saving the rig is a lot less expensive than losing it, not to mention my head.