Whatsapp, the end-to-end encrypted messaging app for the iPhone and Android devices, is now available for Mac OS X 10.9 and higher, and Windows 8 and higher. Apple's Messages offers end-to-end encryption, too, but only with other iOS device and Mac users. Whatsapp encrypts your conversations regardless of which platforms everyone in the chat uses. Think of it kind of like a babble fish for encrypted chats. Whatsapp is free and the desktop version is available for download at the Whatsapp website.
Check It Out: Whatsapp goes Native on OS X and Windows