Twilio - Brings voice and messaging to your web and mobile applications.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Plivo - Plivo simplifies your customer engagement.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Slack - A messaging app for teams who see through the Earth!