WhatsApp is a pretty popular messaging app, although I wound't know as the appeal over the dozen other ones available escapes me. The only thing I really know is that it's always in the news when politicians who don't know thing one about tech (See: Jeb Bush realizing he can take a call on his Apple Watch) talk about encryption and terror. Another thing I know is that it costs you $0.99 a year to use the darn thing.