DialogTech - DialogTech is an end-to-end call attribution and conversion platform.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Invoca - Call tracking & analytics software
Quickie - 3-60 second video calls with your friends
CallTrackingMetrics - Know who is calling and how they found you. Maximize the return on your advertising.
Messenger Video Calls - Facebook Messenger, now with HD video calls