I came to the same conclusion instantly at the moment of my first encounter of a finger magnet idea on YouTube - "Cool, but I want a ring that does that and that I can tune, replace and put on and take off at will...".
The better wearable devices get, the less sense it makes to permanently modify your body. Things like exoskeletons, smart glasses, and external brain-computer interfaces are safer and much easier to upgrade than their implanted counterparts. Plus, you can take them off in inappropriate situations: you won’t get stuck trying to swim with a metal limb, for example, or wearing a permanent version of Google Glass to a laid-back dive bar.
I really think wearables make vastly more sense for enhancing ourselves than this kind of body modification.
Yes, I read the article, that's why I said I came to the same conclusion ("wearables > implantables").
My 'ring' answer for magnet in finger was just an example of a counterpoint in such a debate between these two transhumanism approaches. I of course approve smart glasses, rings, bracelets, wearables, exoskeletons, etc. over implants, surgeries and metal bones (Wolverine from X-Men excluded ;). Of course nanites easily trump wearables but they are way too far into the future at this point I'd think.
I still want a finger magnet, because having it inside your body next to your nerves makes it way more sensitive than any external device could be.
On the other hand, I'd much rather have a North Paw anklet (https://sensebridge.net/projects/northpaw/) than that implanted compass. I love the idea of using technology to augment my body and mind, but that doesn't necessarily require implantation.
On the third (cybernetic) hand, I totally understand the almost fetishistic excitement for full-on cyborgization. If I had to have a limb amputated, that would suck a lot, but getting to customize and show off a prosthetic would be a real silver lining for me. If I could electively replace a healthy hand or arm with a mechanical one that was categorically equal or superior, I would consider it. But I'd never accept a loss of real function just to look cool.
I considered the magnet but the problems are: it weakens over time, might break, might infect you, the scar tissue builds up and disables the feeling and it's still metal in you (MRI, etc.). Pain I'd not mind, it's a brief surgery after all, but some people mind surgeries too.
Alternatively: nanites like in DX1 and DX2.