@jdfwarrior The recipient does not need to have the app installed for you to send them a Confide within iMessage. When they receive it on their iOS 10 device and tap on the chat bubble, they will be prompted to install the app, and then can read the message. They do not need to signup for any account -- it's pretty frictionless. It also supports group chats.
ArtSquare
Alfred
ScreenShieldKit