A key fob (a current implementation) is a better than a ring. You probably already have to have your keys to leave the house (lock door, start car) so it's not another thing to remember. Key fobs are a single standard size and keyfobs don't get tight when you get pregnant or fat. Key fobs aren't uncomfortable, don't give you allergic retractions, and aren't a potential safety hazard like rings are for many "hands on" jobs, and also don't impact hand hygiene.

The benefits of an implant are you, can't forget your implant, you can't lose it, it can't be stolen, and you can't give it to someone else. You also (probably?) can't break an implant.

You can steal or forget a ring, and rings can be uncomfortable for some people.

You can't give your implant to someone else very easily.