I've got an existing Android app that I'd like to provide a wear 2.0 complication for. I do not wish to create a custom Wear Watch Face nor a companion Wear app - I simply wish to be able to create a complication that users should be able to add to an existing watch face. Is this possible? Reading the documentation it seems to me that I would need to create a custom Watch Face or an app in order to provide a complication. I'm now a little confused. Any directions on this would be appreciated.
You don't need to develop a watch face, but you do need an app running on the watch to deliver a complication. It doesn't need any other UI (such as an Activity) unless your complication requires it for configuration, but the ComplicationProviderService does need to be in an APK running on the watch.