I'm not sure if I'm answering the question you have or not, but the additional insurance I purchased for my processor covers loss or damage, including running it over with a lawnmower (as long as I don't do it intentionally!). There were a few exclusions, but they were things like nuclear war, a plane crash, train derailment, etc...odd things. It's basically covered like traditional hearing aids, engagement rings, diamond earrings that get washed down the drain
, or anything of value that you want to make sure is covered for it's full value and not just what the insurance company decides at the time off a loss.
The implanted part itself should be covered by medical insurance - if it needs to be replaced or removed, I would imagine your medical insurance would cover that, especially if they paid for you to have it put in in the first place. It's probably not an issue much, because all it is is a titanium screw with no moving parts, so it's not prone to breakage. A Cochlear implant is a different story, and they actually do fail - in which case, the implanted part is probably covered by medical insurance and the external part would probably need to be covered on a separate personal articles policy, much like the regular hearing aids.
Lori