Meet the Radica Kneeboard: a piece of equipment that combines the experience of water-skiing and wakeboarding to enrich your water adventures. The Radica has cupped molded fins for edging and carving. You can also do fun spin tricks with it. It also has a padded, adjustable knee strap and variable edge bevels
The above video shows the Kneeboard in action. You can get it for $119.99.