Daily.co for Intercom - Free video calls & screen shares embedded in Intercom
Phonebot - Make phone calls from within a Slack channel
Pluot Communications - Big-screen video conferencing for startups
WING - A phone carrier that is actually nice to you.
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.
HideMyFaceTime - Stop watching your own face during FaceTime calls.