Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
StealthChat - StealthChat is Encrypted, Private, Secure Calls and Chats on Android and Apple iOS
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs