Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Green Messenger - WhatsApp Messenger Web for Chrome. Text/Chat on computer. Notifications, messages, tools.
MyChat - Secure instant messenger for any network
WhatsApp Web To Go - WhatsApp Web client for your phone/tablet with media support
Ubiq Security - Enable developers to build encryption into apps in minutes
App for WhatsApp by coldX - Integrated WhatsApp functionality on the Desktop.