What good would it do the Feds to install an app on your phone? Unless you run it, it won't do anything. And even if you do run it, it can only do what its permissions allow so it isn't like it can copy all your info to the Feds, or send them your phone's password (unless it asks for it, and you are dumb enough to provide it)
If they wanted to go through the back door they'd have something like Stuxnet that would probably hack the baseband OS to bug your phone (I wouldn't be shocked if they already have this, at least for popular basebands like Qualcomm's)
They don't want to go through the back door, they are trying to set a precedent that lets them walk through the front door, with everyone watching, and leave us unable to do anything about it.
Biting the hand that feeds IT
