Overuse injuries are also a danger if you're not super careful about how you combine grip training with other activities. For example, we did a lot of overhead weight work (power cleans, snatches, overhead squats, etc.) at Crossfit on Friday and Monday, which puts a lot of strain on my wrists and elbows. I should have skipped my grip-strength training on Tuesday, but didn't, and now I've got ligament soreness in both arms. Now I have to do NO grip training for the next two weeks and taking vitamin I with every meal to manage inflammation.

I have direct personal experience with discovering new and exciting ways to incur overuse injuries. I don't recommend it as a hobby.