There are two use cases here, one is a version of a website optimized for mobile view, the other is an specific mobile application, which can be downloaded from an app store. I guess you are referring to the later here.

In my opinion, what you need here is web content management system, not an fully fledged ECM. This is what FatWire is (now Oracle WebCenter Sites). Using this platform, its possible to expose web views within the application (which essentially renders HTML pages) or pull content via a Restful interface.