The vibrating arm band, called Ghost, detects a user's arm motion and buzzes to give feedback. It would work by pre-loading the wristband's software with the right pattern of muscle movements, or even a certain athlete's exact swing. The pattern includes certain way points, which would indicate where your swing or stroke is going. Then the device would guide the athlete through the motions. Sensors can detect the joints' flexing and twisting, and vibrations and sounds indicate whether the user is doing it wrong or right. With each try, the athlete's muscle memory gets better, but there's no coach demonstrating how to do it and no hours of video to sit through. It could help vision-impaired and fully sighted athletes.