My solution to enabling livereload with connect-assets.

.gitignore

.tmp

app.js

// to be used in jade
app.set('dev', app.get('env') === 'development');

// to be used as temporary folder
app.use('/tmp', express.static(__dirname + '/.tmp'));

Gruntfile.js

module.exports = function(grunt) {
    grunt.initConfig({
        watch: {
            stylus: {
                files: ['assets/css/**/*.styl'],
                tasks: ['stylus']
            },
            css: {
                files: ['.tmp/app.css'],
                options: { livereload: true }
            }
        },
        stylus: {
            compile: {
                options: {
                    use: [require('nib')]
                },
                files: [ {'.tmp/app.css': 'assets/css/app.styl'} ]
            }
        }
    });

    grunt.loadNpmTasks('grunt-contrib-watch');
    grunt.loadNpmTasks('grunt-contrib-stylus');
    grunt.registerTask('default', ['stylus', 'watch']);
};

layout.jade

html
  head
    if local.settings.dev
      link(href='/tmp/app.css', rel='stylesheet')
      script(src="//localhost:35729/livereload.js")
    else
      != css('app')