TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type

Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.

PropelAuth - PropelAuth hosts and manages your authentication.

Recurly - Subscription billing and recurring billing management. Recurly offers enterprise-class subscription billing for thousands of companies worldwide.

Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.

Zuora - Zuora creates cloud-based software on a subscription basis that enables any company in any industry to successfully launch, manage, and transform into a subscription business.