I just read it on web. looked interesting. This guy has a patent describing this device.

A device and method for determining whether or not the string face of a racket is held in a vertical plane as the racket is swung. At least one sensor is attached to a racket. The sensors detect when the string face of the racket is in a vertical plane and when the string face deviates from that vertical plane. An indicator is also attached to the racket, wherein the indicator produces a perceivable indication to the user of the racket wher activated. A logic circuit is used to connect the sensors to the indicator. When the sensors detect that the string face of the racket has wandered from the vertical plane, the indicator is activated and the player holding the racket is informed of the lapse in form. By repeatedly swinging the racket and trying to avoid activating the indicator, a player can train to have a proper level swing.

so basically it just detects when the racquet face is perpendicular to the ground? You can purchase sensors like for awhile now. His just includes mounting for a badminton racquet. I think the device is too large/heavy right now to be useful.

so basically it just detects when the racquet face is perpendicular to the ground? You can purchase sensors like for awhile now. His just includes mounting for a badminton racquet. I think the device is too large/heavy right now to be useful.

yes, basically by vertical position, it means whether or not the string face is vertical to central imaginary plane. Just to make sure, you are hitting the birdie straight and not chopping at an angle..

mainly would be used while you are learning to hit shuttle correctly. And you won't need a court or birdie to see the effect of your swing action... :)

no, i don't think device would be large... if the sensor is embedded in the racket frame, then it just like a normal racket...

Most players would not need this as they would be either able to see if they have hit the shot not on centre if it slices one way or the other or just feel it as they impact the shuttle.