SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Twilio - Brings voice and messaging to your web and mobile applications.
Recurrr - Send recurring emails
Plivo - Plivo simplifies your customer engagement.
Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.