Smooch.io for Facebook Messenger - Message your customers from Slack, Front, a bot or anywhere!
GetChat.App - Add WhatsApp chat to your website for free
Textedly - Textedly is an SMS marketing communications channel that allows to advertise, promote, announce, and engage with audience through text messaging directly to cell phones.
Avochato - Text messaging for your business.
BlueReceipt - Text marketing customers love ❤️
Talkus - Chat with your website users from Slack