I've been keeping close tabs on the project for a while now and it seems that version 1.8, which should be released in a few days, has the beginning of a rudimentary API. It also looks like more endpoints are being planned for subsequent releases
You can always expose the REST API. Its pretty easy considering they are just flask blueprints. Since, you can make your own custom plugin - You can build a lot using existing infrastructure that Airflow provides.
We're working on moving more functionality to a REST API - there's already some code for this in master :)