Twinme - Twinme – Private Messenger is a free, secure, instant, and high-definition messaging app that protects your privacy along with giving you full control over each of your relationships and contents.

Snarl - Snarl is a notification system for Windows.

Textra - Textra is a seriously beautiful, feature rich SMS and MMS app.

Notifu - Notifu, a free open source pop-up balloon utility

Material Messaging - Material Messaging is a beautiful communication app that lets you send and receive SMS and MMS messages using the intuitive interface while giving you complete control over every aspect of your messaging experience.

Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.