Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Visible - Visible is a wireless service by Verizon that offers unlimited data for a small price and enables you to earn a few bucks by referring friends.
TextMe - TextMe is a free calls and messaging application at both local and international levels.
Fonoster - A marketplace where local telecom companies can publish numbers, developers can build voice, video, and chat solutions.
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.
Sendbird Calls - High-quality voice and video calls inside your app