How to get notified about change in Cosmos DB through ChangeFeed?

When I'm browsing through MSDN documentation all I can see is "observing" changes on ChangeFeed. Even the first diagram there shows only direction from external services (Storm, Azure Functions, etc.) towards ChangeFeed.

Is there any pattern that (is not obvious for me) we can use for getting notified about changes in Cosmos DB over ChangeFeed? Or there really needs to be support built-in e.g. Azure Functions to get this "PUSH" scenario working?

Thanks a lot