Reasonably well. The magnets aren't very strong, so the device in question pretty much has to be stationary while it's charging, also, while most of them allow data, it is almost always USB 2 speeds. Right now I'm using them to charge headsets, a Logitech trackball, and provide data for an Xbox controller.
I get them from Amazon; " magnetic USB charge wire" should be a sufficient search to get you in the ballpark.
My state has a 'Ron' but otherwise I'd have suspected they were the same person, based on the description.