Prometheus is the flagship of modern open source monitoring software for server infrastructure.
Messaging from inside Prometheus is done via the integrated Alertmanager. Since it does not come with a built-in SMS function, it has to be extended via a plugin. This is where Sachet comes into play, where Sms77 is integrated as a message provider.
Sms77 for Sachet allows you sending SMS as well as text-to-speech messages. You can set a custom caller ID in both cases. Please consider the regular regulations here. You also have the possibility to enable debug mode which acts like a sandbox.