public class MyPlugin implements Plugin {
    @Override
    public void define(Context context) {
        context.addExtension(MyPostAnalysisTask.class);
    }
}

public class MyPostAnalysisTask implements PostProjectAnalysisTask, Sensor {

    private String param = "";

    @Override
    public void describe(SensorDescriptor descriptor) {
        descriptor.name(getClass().getName());
    }

    @Override
    public void execute(SensorContext context) {
        // Get command line param.
        Optional<String> param = context.config().get('my.param.name');
        if (param.isPresent()) {
            this.param = param.get();
        }
    }

    @Override
    public void finished(final ProjectAnalysis analysis) {
        if (!this.param.isEmpty()) {
            // Perform custom post analysis task.
        }
    }
}