Twilio is a web-service API that lets you use your existing web languages and skills to build voice and SMS applications. We focus on building a simple, powerful, pay-as-you-go communications platform so that you can focus on what you do best.
Plivo is a voice and SMS API platform that enables developers and enterprises to build powerful apps with great features. With 24/7 free tech support and low prices, Plivo can help your business scale globally.
WhatsApp is a popular messaging platform around the globe. With Maytapi you can send and receive messages from WhatsApp using simple HTTP requests. Integrate your marketing or business platform (Shopify, Woocommerce, CRM ets.) to WhatsApp easily.This app doesn't have any features at the moment.
A private / encrypted SMS phone number in the cloud.
Multiple people have reported that this service doesn't work correctly, so be aware before using it: https://www.producthunt.com/posts/crypton-sh-sms
Flashy helps you get to know your contacts and deliver to each one of them the right message at the right time via email, SMS and Push notifications in applications and web browsers.