Plugins
If you want to create your own checks instead of working on the original repo, you can simple let your checks implement the Checkable interface or extend the abstract Check class (which implements the Checkable interface, but might not be suitable for every use case), then merge your checks into the audit.checks config array.
You can also not implement the interface if you want to have another return type, all checks in audit.checks that contain an execute function will be executed with no arguments. Note that you will not be able to have colored output in the artisan command for other status values.