I'm not quite sure what the benefit is of using this versus using an AW on your wrist. I guess it makes the device more discreet and discourages usage. But for me, one of the reasons I like my (non-AW) smartwatch is that I can't reliably tell when my iPhone has buzzed in my pocket. If I put an AW inside a rubber case and stuck that in my pocket, I'd probably have a hard time telling when it vibrated.
Yet, I am still somewhat intrigued by this device...