API to send message

Hello! I'm trying to figure out a way to send alerts to a channel via API. I was able to authenticate to the API using credentials from a Server-Server OAuth app however I'm now reading that only user accounts can send messages (using /im/me/chat/messages/Send IM messages ) and I can't grant this app access to send messages. Is there any other way to automate sending messages to a channel or person? I've read some about chatbots but I'm also not trying to sign up for a bunch of third party stuff and worry about confidentiality. 

Thanks!