Would a wireless (stringless) Yo-yo be possible? I have this interesting idea for a toy (not a real one, it's for a story). It's a stringless yo-yo that uses electromagnetism to mimic a regular yo-yo.
The user wears a ring on their middle finger with a small magnet inside in that controls the yo-yo. The ring and yo-yo use opposing magnetic forces (don't know the actual term) so the yo-yo looks like it levitating above the users' hand. When the user moves their hand, the ring uses sensors to move the yo-yo in a way that makes it look like it's on an invisible string. If the yo-yo is "thrown" too far it'll just fly back. The only downside to having it is you can't really preform tricks like with a regular yo-yo.
My question is would this be possible, or is it too complex for a toy?
 A: The fundamental difference between your idea and a real yo-yo is that the further you stretch a string, the greater the force it applies to pull the yo-yo back toward your hand.
But with electromagnetic forces, the further the yo-yo gets away from the ring, the less force it would be able to apply to bring the yo-yo back. This would fundamentally alter the way the "yo-yo" behaves and make it very difficult to have the magnetic device act like a traditional yo-yo.
Conceivably you could have the ring contain an electromagnet, and drive it harder, the further it gets from the yo-yo. But because you're fighting against the natural behavior of the forces involved, you're going to have "difficult engineering challenges" (which is engineer-speak for "I don't think you'll be able to get it to work") doing it.
Think about this: Have you ever played with a magnet that was able to produce a significant force on an object from more than a few centimeters away? Probably not. There are such magnets, but they get pretty dangerous since to be able pull on small objects from far away they have to be able to pully really damn hard on objects that are nearer, and you could easily lose a finger or more if you got it between the magnet and the object it was acting on.
