@shortstories This is actually stupid...
Think about the process for a minute...
Instead of using an equipment, that create a predictable and fluid motion to work your muscles, you opt for this magnet idea, where you just keep exerting your strength, until you randomly experience a snap release. This is what you do, when you want to use your strength, not when you're training your muscles. And just because it's easily repeatable, won't change this.
Is he going to play with suction cups next?