We started developing a python3 client library to exchange data with a ODK-X sync endpoint server.
Currently its in early stages, and available here: https://github.com/Kapernikov/odkxpy
It supports querying the server, and downloading/uploading to/from a local PostgreSQL datastore.
It only has very limited setup for creating interactive applications (that's not why we created it).
We use it to integrate ODK-X into a workflow where some data fields are updated by computations or external databases.