Snarl - Snarl is a notification system for Windows.
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
TextMe - TextMe is a free calls and messaging application at both local and international levels.
Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
Talkatone - Android App on. Google Play. Stop paying for cell minutes, texts & landlines; Turn your iPad or iPod touch into a phone; Call/Text even in areas with bad cell coverage; Call/Text when travelling without paying for expensive international minutes.