It's not clear for me from the docs. Is it possible for a mobile app to be data provider for complications or I must have a standalone wear app?
Here's an information regarding data provider for Android Wear. "A watch face never has direct access to a data provider. It will instead receive a callback when new data is available for the complications that the user has selected. Meanwhile, the data provider doesn’t know how the exposed information will be displayed: That is completely up to the watch face, depending on its style." You can check this blogpost for more details.