Planet Waves says its Varigrip is the "perfect tool for pre-show warm-ups and maintaining conditioning when away from your instrument." So, yeah, it's totally a hand job trainer. Both for masturbatory efforts and those administered by others alike. Ahem, ladies, take note: bonus points are awarded for a strong grip and deliberate fingers.
I guess the Varigrip is also good for the other kind of people who play instruments: musicians. The hand exerciser has adjustable tension levels for each finger, enabling users to focus on and strengthen their digits individually. The intended effect is to improve overall dexterity and muscle power in not only the fingers, but also the hands and forearms. Working fingers separately also prevents strummers and key depressors from favoring pointers of pinkies, tallmen over ringmen, and thumbs over piggies that cried wee, wee, wee all the way home.
The Varigrip is comfortable to use with its over-molded finger pads and grip, unless you opt to hone your discomfort by removing the reversible grip to reveal a simulated string for developing and maintaining finger calluses.
The Varigrips hand exerciser is a top Dude Gift for a Musician pick.