Grunt configuration for using nodemon and output logs with Bunyan

Gruntfile.js

module.exports = function(grunt) {
  require('load-grunt-tasks')(grunt);

  grunt.registerTask('default', 'concurrent:dev');

  grunt.initConfig({
  
    concurrent: {
      dev: {
        tasks: ['nodemon:dev', 'watch:js', 'watch:sass'],
        options: {
          logConcurrentOutput: true
        }
      }
    },
    
    watch: {
      options: {
        atBegin: true,
        spawn: false,
        interval: 1500
      },
      sass: {
        files: ['theme/scss/**', 'theme/images/**'],
        tasks: ['compass:dist', 'copy:images']
      },
      js: {
        files: ['theme/templates/**', 'front/**/*'],
        tasks: ['ngtemplates:ideation', 'concat:dev'],
        options: {
          interval: 500
        }
      }
    },
    
    nodemon: {
      dev: {
        script: 'index.js',
        options: {
          stdout: false,
          watch: ['app'],
          callback: function (nodemon) {
            var bunyan;
            nodemon.on('readable', function () {
              // free memory
              // bunyan && bunyan.kill()

              bunyan = grunt.util.spawn({
                cmd: './node_modules/bunyan/bin/bunyan',
                args: ['--output', 'short', '--color']
              }, function() {});

              bunyan.stdout.pipe(process.stdout);
              bunyan.stderr.pipe(process.stderr);

              this.stdout.pipe(bunyan.stdin);
              this.stderr.pipe(bunyan.stdin);
            });
          }
        }
      }
    }
  });
};

Update for providing a done callback for the spawn process (http://gruntjs.com/api/grunt.util#grunt.util.spawn)