The ActivityInfo API allows you to query and update public and private ActivityInfo databases. You can also push updates to ActivityInfo databases for which you have write permissions.
ActivityInfo offers a JSON-based API that mostly follows RESTful principles, so you can either use your favorite REST client library to send and receive JSON, or you can use a client library for R for convenience.
Note that our web-based client and mobile apps are also built on this API. That means that anything that can be done through the user interface can be automated through the API.