If Apple allowed removable batteries, this could be avoided.
Heck, even the chinese produce better (and much cheaper) machines and more robust OS's!
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.