Twilio - Brings voice and messaging to your web and mobile applications.

Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates

tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page

VoxSciences for Offices - VoxSciences for Offices converts the voicemails lon office phone into text and delivers them to an email or SMS text message.

JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website