WikiPro - All-in-one Business to Customer Communication
Avochato - Text messaging for your business.
Heymarket - The professional way to text message. Your customers are mobile. Heymarket helps you manage those relationships from your smartphone.
Message Me - Website to create your contact business card
Text Groove - Text enable your existing business landline, VoIP, or toll free phone number and connect with your customers in a whole new way. Try Text Groove for free.
Slack with your Users - Speak to your app's users entirely within Slack