accessing wix data, initiated from another source?

We’d like to use wix for a custom built application. We would really need to access data stored in wix’s datastores, put data in there from other servers / services, manipulate data and read data in wix datastores. This is possible with JS hooks, as i read, but we’d like to authenticate and effectively initiate all access from other sources. Since our application will be server-driven and the wix-site would merely be one of the access portals.
Is accessing wix data, initiated from another source, possible in any way? or would we need to get authentication & all datastorage off of wix to get the needed functionality?
More consise: Would it be possible to initate a request to receive all currently registered usernames and telephone numbers from our wix site? Authenticate with credentials, perform (SQL) Queries, and put un-gathered phonenumbers that we received via another portal back in wix datastores?

Yes, you can create your own web-service API. Take a look at wix-http-functions for the details.