In practice, it's a bit tricky as the corn cob can slip from its position, and the kernels can go flying all over the place!
I don't know where I first heard of this trick of using a bundt pan, but it's great for helping to steady the corn cob and to catch the kernels as they come off the cob.
Easy Tip for Getting Corn Off the Cob
1 ear corn
To remove corn kernels from the cob using a bundt pan, stand the shucked corn cob upright, with the tip of cob placed in the center hole of the bundt pan.
Holding the cob steady, use a sharp knife and make long downward strokes on the cob, separating the kernels from the cob.
Many bundt pans have a stick-free interior. If this is the case with yours, be careful not to scratch the interior of the pan with your knife. If the knife scratches around the edges of the bundt pan hole, that shouldn't be a problem, as when you use a bundt pan baking, this area doesn't usually come in contact with the cake batter. (Note from the comments, you can tuck a paper towel or dish towel into the hole to protect the pan.)