I would like to see the ability to share specific contexts with people, both on the running tracks instance, and via the REST API, using an authentication token, like google does for its ical API.

That way, you can integrate non tracks users, on other systems, without giving access to your whole tracks database.
I.E. having to sync everything

I'm guessing this is a change/addition to the REST API authentication mechanism, and possibly adding local/remote tracks<->tracks server sync via REST