@dawnlike history-service is the code that store and retrieve SMS. But notifications of new SMS is managed by telephony-service. Communication between them is handled through dbus with a middleware called Telepathy. So you might listen to dbus signals if you want to be notified of a new sms. If it helps: https://m.youtube.com/watch?v=5b3PGvDbcp8 https://m.youtube.com/watch?v=IGgbEhTrmvg