We need to defend our digital rights! And one of the best ways is to code up tools to show where and how privacy, free speech and technical transgressions are taking place. Transparency is the first way to show what problems exist and how we can deal with them.
Your idea may be about public education. It may be about documenting abuses we already know about. Or it may be about circumventing the problem and reasserting your rights.
There are a myriad of possible things we can do. and the day has no restrictions on what you code or do. The big themes are