How do I define a "remote variable" for use with Oculus Remote Monitor?

Oculus provides a nifty test/profiling tool called Oculus Remote Monitor. The docs say:

Applications may expose user-adjustable parameters and variables in their code. Nearly any constant in your code may be turned into a knob that can be updated in real-time during a play test.

But nowhere can I find any documentation on how you actually expose such a parameter/variable. How do we do this?