I use Firebase pretty extensively and have a fairly large app using it.
In your case, Firebase would replace PostgreSQL and Django would make API calls to Firebase instead.
So if you don't want to rip out PostgreSQL and start over - you'll have to make the backend make API calls to Firebase to write the data you want to be realtime (in addition to possibly writing it to PostgreSQL) and then the Android app reads from Firebase.
There is a python wrapper - https://github.com/mikexstudios/python-firebase
And if all else fails - strait up curl works also.