i bought one of these for my bf for last christmas, among many other things. Its a gyroscope, basically a little spinning thing inside a ball that you hold onto which revs really high and creates a g-force within your hand. Controlling it while its spinning enhances your forearm and wrist. www.powerballs.com has more information. lookss like a toy but once you use it its like, whoa...
lol.. yeah well the boy is using it :P apparently also good for mucisians and people who play sports where you need strong wrists ie golf, baseball, tennis...