What are some alternatives?
NextPlane - NextPlane offers cloud-based, scalable unified communications federation service for the enterprise.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
SightCall - SightCall offers comprehensive real-time video APIs and Mobile SDKs that makes it simple to embed...
Beekeeper - The #1 All-in-One communication & productivity platform used for reaching and connecting every individual in an organization.
Voxer - Turn your phone into a Walkie Talkie. Don't waste time on phone calls and voicemails.
Jive - Jive's Hosted VoIP UC platform is an enterprise-grade business phone system that works for any organization. Welcome to Unified Communications in the cloud.