You know, there's a LOT of easy to do exercises that will increase your wrist, grip, forearm, all the way through shoulder strength... one of the easiest is to simply buy an 8 pound sledgehammer... choke up on the handle so you're near the head... mark with a sharpie where you are holding... then while holding the sledge straight out in front of you at about shoulder height, turn the hammer left and right for reps... do the same with the other hand... then back to your other hand, move the hammer forwards and all the way back to the shoulder (like you're hammering something). Do this twice a day.
Once you're able to do 20 reps, both ways and with both hands... move down the handle an inch, and mark with the sharpie... if you stick to it, within a couple of months you'll be a LOT stronger from the ends of the hands all the way into your shoulders and back.
Like I said, there's many ways to get stronger... but this is one of the best.
If you would like to go to the next level in this kind of strength... let me suggest checking out: http://www.davidhorne-gripmaster.com/forum/index.php
it's a forum dedicated to grip and overall strength, and it contains a LOT of useful information!