how to send a message from a browser to the ioHub?

Thinking about how to pass events (e.g., URL change) from the assessment webpage to the ioHub. In this case we assume the subject is interacting with a browser window, in which we have a custom javascript function that gets the timing of certain events (e.g., changing from one item to the next), and we want to pass that event as a time stamped message to ioHub.

What's the best way to do this? This is not part of this deliverable but I'd like to hear your thoughts.