WikiPro - All-in-one Business to Customer Communication
TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type
Heymarket - The professional way to text message. Your customers are mobile. Heymarket helps you manage those relationships from your smartphone.
LoginRadius Authentication - Secure and robust authentication, SSO with user management
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.
Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.