HelpStack - Open Source mobile help framework to support iOS and Android app users.

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

Chat Center - Chat with one click, no matter what messaging app you use

Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors

Helpshift - Helpshift is an in-game customer support platform that enables mobile apps to improve customer experience, drive higher ratings and increase retention.

Zendesk for Startups - Everything you need for seamless customer conversations.