Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Keybase Chat - End-to-end encrypted chat built into Keybase
MyChat - Secure instant messenger for any network
Crypho - End-to-end-encrypted messaging and file sharing
Ubiq Security - Enable developers to build encryption into apps in minutes