Secure instant messaging system for team collaboration
Twilio - Brings voice and messaging to your web and mobile applications.
LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Softros LAN messenger - LAN messenger for an internal office chat for home or business users. It does not require a server and is very easy to install and use. It supports personal chats, group chats, message brodcasting, files transfer and remote desktop access.
Clockwork SMS - Clockwork is an Easy Text Message API. An SMS API for Developers. Build powerful apps and include SMS. Signup is free, Try it now.
Bopup IM Suite - Organize secure messaging system and communicate instantly via self-hosted IM server.