I've built a SMS to Slack which enables two-way SMS messaging from your Slack channels.
I had an annoying use case where when trying to login to a shared work account, the 2FA code was being sent to a colleague's phone number. Now being able to receive that code in Slack solved the problem.
Customers now use it for their own customer support. End users really like SMS as a messaging platform, nobody wants to send an email or talk to a chatbot.
It uses Elixir, Fly, GCP, Stripe, and a couple carriers.