Meet the SPK-1: a solar powered outrigger attachment that lets you use the sun to propel your kayak thorough the water. It is designed for folks who are either tired of paddling or have a disability that keeps them from doing so. Just attach it to your medium/large kayak, and you are set. The battery is charged with sunlight, which in return powers a 12V motor. You don’t need to make any major modifications to your kayak to get started.
The SPK-1 has an aircraft grade aluminum frame and mounting brackets that should conform to most medium and large kayaks. The kit includes a frame, motor, battery, solar cells, and a 120V charger. Sets you back $1100 + s/h.