You can check yourself. Like in the article, stick a gizmo in your ear and that listens to what the nanites broadcast, and then you decide to see a doctor based on that.
Can it be abused? Sure it can. But then, so can everything. Is that reason not to use it? No. Think what would have happened if people had thought "I've come up with the concept of a hammer! It'll be great, I can use a hammer to help build things! Or I could use it to bash someone's skull in. So because the technology can be abused, we mustn't invent it."
There's risks in everything. Maybe some of the things that we're coming up with are more risky than a hammer, but if go down that path we'll just end up sitting on our hands for fear of doing ANYTHING, and we get nowhere. I'm all for rational and reasoned ethics, but not for irrational fear and paranoia and extreme "what if" situations.