Bailu Taiji wrote:

Eagle catcher.
I'm not sure who is modeling this eagle catcher but they have really thin wrists

. It looks like a good tool though (not that I have had a chance to use one).
Any heavy weapon training is good for improving your wrist and finger strength. Not even heavy weapons actually, just things you need to keep a constant grip on. Kendo seems to work really well for this kind of thing. One of the school principals I worked with was an 8th dan in kendo (currently the maximum achievable level) and he almost crushed my hand the first time I met him. He retired this year so pretty damn good for an old timer. Imagine what he was like in his prime.