ThinkGeek has a variety of interesting items (at least if you’re the geeky sort).  I bought a Powerball last week, which arrived yesterday.  It helps build wrist and arm muscles through the force of the gyroscope.  You start it spinning and then through wrist motion you impart more energy to the gyro.  As it spins faster it takes more and more force to make it go faster.  It’s kind of addictive because you end up trying to beat your own speed record (it includes a digital readout that records your highest RPM). 

I’m not sure how helpful it will ultimately be, but it’s fun to play with.