What part of "This requires PHYSICAL ACCESS TO YOUR iPHONE TO INSTALL HARDWARE" do you fail to understand? Without having prior access to the iPhone, NSA cannot do this. If they can get physical access to your phone, they can install hidden power sources, hidden microphones, etc. All bets are off. Hell, if they've had access to your phone they OWN you.
If you worry about this, simply turn on AIRPLANE MODE. . . which turns off ALL RADIOS. This has been checked. No RF comes from the iPhones at all. Another solution. You want to talk about something you don't want the government to hear? Put your phone in your microwave oven. Excellent Faraday cage. Almost every home has one.
And yet, if I mention that it would be nice if iPhones have a removable battery, you go ape and respond as though your honor had been personally attacked. Get a grip, man! Steve Jobs told people who had antenna problems that they were holding the phone wrong. You suggest putting the phone in the microwave. Both ridiculous of course. The fact is, Apple makes such choices to prevent the user from having more control over the device, and of course, to maximize profits. Apple hates when third parties make accessories that allow them to make a buck, and so they create proprietary cords and work hard to make working on an iPhone, iPad or Macbook Pro as difficult as possible for non-Apple techs.
Many of us know this and buy Apple products in spite of it. There are many things people like me love about Apple. But I, unlike you apparently, admit of the possibility that Apple may not be perfect. It is a choice, with tradeoffs, and one of those tradeoffs is, they HAVE to control everything. Including batteries. There are many reasons why a removable battery is nice, and NSA spying through the microphone (whether they have to have PHYSICAL ACCESS TO YOUR PHONE or not, is just one of many.
Have a great day.
--written on Macbook Pro Retina
Turning the microwave on while the phone is in there is an excellent way to make sure the feds won't be able to use your phone to track you any more.