Sorry but having an NSA proof to make people feel better because their traitor hero Snowden told them the evil goverment is spying on them isn't going to do squat when they tweet the world that their boss Mr. X is a so and so or that picture of their junk they thought was NSA proof gets automatically backed up to Google+ and put on their public profile.
: If we are talking about the security and the privacy we have to mention about eavesdropping (like you did). To encrypt emails, texts and calls, you don't need to buy Blackphone. There are a professional apps and software available on the market. One of them is mySecurePhone. It's designed for any smartphones with Android. Additionally, it is compatible with any email account, so allows you to keep your favourite one.